9th.
World
Congress on Parasitic Plants
Charlottesville,
VA 3-7
June 2007
Ahom,
RI, and Okereke, OU.
Varietal Differences in
Ability of Sesame and Pigeon pea as Trap Crops to Induce Suicidal Seed
Germination in Striga hermonthica
(Scrophulariaceae)
Alejandro
Pérez-de-Luque. Mechanisms of Resistance to
Parasitic Plants: from Field Screenings to Laboratory Microscopic
Studies
Alers-Garcia,
J, and Bever, JD.
Size Dependent
Parasitism of Cuscuta gronovii:
Its Implications on Host Population Size Structure and Dynamics
Alers-Garcia,
J, Lewis, KC, and
Wright, LJ. Parasite
Mediated Maternal Effects in Bitter and Sweet Lupins
Aly, R, Shomin, H, Joel, DM, Steinitz, B, Zelcer, A, and Gal-On, A. A New Approach to Parasitic Weed Control Based on Silencing of a Key Metabolic Gene in the Parasite
Aouali,
S, Bouznad, Z, Zermane,
N, El Khishine, D,
Madkour, M, Faied, M, Chaabane, M. Genetic Diversity Among Orobanche
crenata
Ecotypes Revealed by RAPD and AFLPs Markers, in
Algeria
Bewick,
TA., and Cascino, J.
Development of a
Biological Herbicide for Control of Cuscuta spp.
Bolin,
JF, Tennakoon, KU, and
Musselman, LJ. Stable
Isotope and Nutrient Relationships of the Root Holoparasite Hydnora
(Hydnoraceae) in Southern Africa
Bouwmeester,
HJ , Cardoso, C,
Zhongkui, S, Matusova,
R , Lopez-Raez, JA, Charnikhova, T, Verstappen, FWA , Rochange, S,
Bécard, G,
and Ruyter-Spira, C. Strigolactones, Signals for Friends and Enemies
Cameron, DD, Keith, AM, and Seel, WE .Rhinanthus minor as an Ecosystem Engineer: Understanding the Mechanistic Basis of Parasitic Plant-Induced Changes in Community Structure.
Castillejo,
MA, Maldonado, AM,
Dumas-Gaudot,
E, Pérez de Luque, A, Rubiales, D, and Jorr’n, J.
Differential
expression
proteomics to investigate responses and resistance to Orobanche
crenata
in legumes
Chachalis,
D, and Murdoch, AJ.
Potential Use of
Nijmegen-1 and Smoke Water Solutions to Deplete Orobanche
ramosa Seed
Banks in Greece
Chiang,
MY, Hsieh, YC, Yuan, CI,
and Lin, FY. Cuscuta Species in Taiwan: Molecular
Differentiation and
Related Findings
De
Mol, M, and Heller, A Sap
Flow from Host to
Mistletoe: an Anatomical Approach
de
Zélicourt, A,
Letousey, P, Thoiron, S, Montiel, G,
Simier, P, and Delavault, P. Molecular analysis of resistance
mechanisms
to Orobanche
cumana
in sunflower
dePamphilis,
C, McNeal, J, and
Zhang, Y. Genome
Evolution in Parasitic Plants: New
Genomes, Surprising Findings
Dewaele,
D, Elsen, A, and
Obiudoh, CA. A Study of
Biodiversity of African Radopholus Similis In
Uganda.
Dhanapal,
GN, Borg, SJ ter, and
Struik,
PC(3)Integrated Management of Broomrape in India
Draie,
R, Pouvreau, JB,
Véronési, C, Théodet, C,
Thoiron, S, Delavault, P and Simier, P. The Sucrose-Degrading Enzymes
in Orobanche
ramosa.
Characterization and
Involvement in Growth, Cell Wall Synthesis and Starch Accumulation.
Dubé,
M-P, and
Belzile, FJ. Genetic variability among
five races of Striga gesnerioides
(Willd.) Vatke detected by ISSR, AFLP and cpSSR analysis.
Dunlavey,
R, Logan, BA and
Reblin, JS. The Influence of
Arceuthobium pusillum Infection
on the Hydraulic Architecture of White Spruce Stems
Dzomeku,
IK, and Murdoch,
AJ. Studies on Seed Dormancy,
Germination and Seedling Emergence of Striga Hermonthica
Echevarr’a-Zome–o,
S, Pérez-de-Luque, A, Jorr’n, J,
and Maldonado, AMHistochemical analysis of defense responses involved
in
resistance of sunflower ( Helianthus annuus ) to Orobanche
cumana
Eizenberg,
H, Ephrath, J, Lande,
T, Achdari, G, and
Hershenhorn, J. Temporal Thermal and Special Model for Orobanche
Management.
Elzein,
A, Fen, B, Kroschel, J,
Marley, P, and
Cadisch, G. Synergy Between Striga-
Mycoherbicides
"Fusarium oxysporum f.sp. strigae" and
Resistant Cultivars Under Field Conditions: Step Towards Integrated Striga Control in Africa.
Elzein,
A, Kroschel, J, Fen, B,
Marley, P, and
Cadisch, G. Compatibility
of Striga-Mycoherbicides with Fungicides
Delivered Using Seed
Treatment Technology and its Implication For Striga and Cereal Fungal Diseases Control.
Fan,
ZW, Buschmann, H, Shen, YD,
Lu, Y, and
Sauerborn, J. Induced Host Resistance as a Control Method for Parasitic
Weeds
Fernández-Aparicio,
M, Flores, F, Pérez-de-Luque, A
and Rubiales, D. Yield losses in pea as a function of Orobanche
crenata
levels of infection.
Fernández-Aparicio,
M, Pérez-de-Luque, A, and
Rubiales, D. Response of Medicago truncatula
Accessions to Various Species
of Orobanche.
Fernández-Aparicio,
M, Pérez-de-Luque, A, Sillero, JC
and Rubiales, D. Yield increase in oat-faba bean intercrops under heavy
Orobanche
crenata
infections.
Funk,
H, Berg, S, Krupinska, K,
Maier, U and Krause,
K. Complete DNA Sequences of the Plastid Genomes of Two Parasitic
Flowering
Plant Species, Cuscuta reflexa
and Cuscuta gronovii.
Gebeyehu,
S, Belayneh, A and
Tesfamariam, M. Parasitic
Weeds in Ethiopia: Challenges to Resource Poor and Small Scale Farmers.
Gharib,
C, Haidar ,MA, Sleiman,
FT. and Sidahmed,
MM. Germination and Viability of Cuscuta spp.
(Dodder) Seeds after
Digestion in Sheep Rumen.
Goldwasser,
Y, Yoneyama, K, Xie,
X, and Yoneyama,
K. Identification of the Stimulants Produced by Arabidopsis
thaliana
Responsible for the Induction of Orobanche Seed
Germination.
Gunathilake,
P, Tomilov, A,
Tomilova, N, Fillapova, T
and Yoder, JI. Macromolecular Trafficking from Host Plants into the
Hemiparasitic
Plant Triphysaria versicolor.
Haddad,
A and Pala, M.
Significance of Parasitic Weeds
for Food Legumes in Syria.
Harrison,
MJ. The Arbuscular
Mycorrhizal Symbiosis;
Genomics Approaches to Dissect Development and Function.
Heller,
A, Elzein, A, De Mol, M,
Kroschel, J and
Cadisch, G. Colonization of F. oxysporum f.sp. strigae
(Foxy 2) on
roots of sorghum plants and its implication for Striga
control using a seed treatment
delivery system: an
anatomical study.
Hšniges,
A, Ardelean,
A, and Wegmann, K. Ecological
and Physiological Investigations on Orobanche
Species in the Spontaneous
Flora of Romania
Kaldenhoff,
RWE. Molecular
Events During Cuscuta Infection.
Kanampiu, F. Striga Weed
Management Options
under Smallholder Agriculture in Africa.
Kusumoto,
D, Yoneyama, K,
Yoneyama, K, Takeuchi, Y.
Induction of Systemic Acquired Resistance in Root Parasitic Weeds.
Lanini,
WT, Miranda, M, and
Aouali, S. Dodder (Cuscuta
pentagona)
Control in Roundup Ready
Alfalfa.
Liu,
Y, Liang, L and Lynn DG.
Gene Regulation during
Haustorial Development and Shoot Initiation in Striga
asiatica.
Lopez-Raez,
JA, Charnikhova, T ,
Gomez-Roldan,
V, Matusova, R , de
Vos, R,
Schipper, B, Verstappen, F , Bino, R , Becard, G, and Bouwmeester, HJ.
The
Biosynthesis of the Tomato Germination Stimulants is Promoted by
Phosphate
Starvation.
Lozano-Baena,
MD, Lindsey, K,
Moreno MT, Rubiales, D,
and Pérez-de-Luque, A. Laser Capture Microdissection (LCM):
New Technologies
Apply to Study of the Parasitic Plant Interactions.
Lozano-Baena,
MD, Moreno, MT,
Rubiales, D, and
Pérez-de-Luque A. Analyses of Medicago truncatula
Resistance Against Orobanche
crenata
Using Citochemical Techniques.
Matusova,
R , and Bouwmeester,
HJ. The Strigolactone
Germination Stimulants of the Plant-Parasitic Striga
and Orobanche spp are Derived from the
Carotenoid Pathway.
Miegel,
D, Hayton, D, and
Matthews, JM. Seedbank and
Seedbank Management of Orobanche ramosa in South
Australia.
Murdoch,
AJ, and Kebreab.
Predictive Empirical Modeling
of Parasitic Weed Life Cycle.
Nickrent,
DL, and Vidal-Russell,
R.The Evolutionary
Origins of Aerial Parasitism in Santalales.
Ogbebor,
NO, Omorusi, VI and
Evueh, GA. Evaluation of
Mistletoe Incidence on Nine Rubber Clones and its Effects on Latex
Yield in
Nigeria.
Okazawa,
A, Wada, Y, Fukusaki,
E, Yoneyama, K,
Takeuchi, Y, and Kobayashi, A. Trehalose Promotes Seed Germination of a
Holoparasitic Plant, Orobanche minor Sm.
Pacureanu-Joita,
M, Raranciuc,
S, Procopovic, E, and
Sava, EAO - 548, a Sunflower Inbred Line, Carrying Two Genes for
Resistance
Against a New Highly Virulent Romanian Population of Orobanche
cumana.
Palmer,
AG, Liang, L,
OÕMalley, R, and Lynn, DG.
Calcium Mediated Transduction of Haustorial Inducing signals in Striga
asiatica.
Palmer,
AG, Liang, L, Keyes, J,
and Lynn, DG. ROS
production and Semagenesis in Pathogenesis.
Palmer,
J. Horizontal Gene
Transfer Gone Wild in
Parasitic and Other Flowering Plants.
Plakhine,
D, Tadmor, Y, Levin, I
and Joel,
DM. Non-Stimulated Spontaneous Germination of Orobanche
is Genetically Controlled.
Riches,
CR, and Mbwaga, AM.
Green manure: A Striga Management Technology Whose
Time Has Come?
Roney,
JK, Khatibi, PA,
Stromberg, VK, and Westwood,
JH. Trafficking of Host mRNAs into Dodder: A New Frontier in
Host-Parasite
Communication.
Saadoun,
I, Hameed, KM, Ababneh,
Q, Bataineh, S and
Foy, CL. Biological Control of Orobanche
cernua
Seed Germination Utilizing an Indigenous Actinomycete Isolate in Jordan.
Sandler,
HA. Integrating
Germination Patterns,
Chemical, and Nonchemical Options to Manage Swamp Dodder in
Massachusetts
Cranberry Production.
Schneeweiss,
GM, Park, JM,
Manen, JF, and Colwell,
AE. Phylogeny and Evolution of Orobanche and
Related Genera
(Orobanchaceae).
Scholes
J., and Press, M. The
Molecular Basis of
Susceptibility and Resistance to Striga: insights
from Transcript
Profiling.
Shamoun,
SF, Rietman, LM, Askew,
SE, and van der
Kamp, BJ. Development of a Biological Control Strategy for Management
of Hemlock
Dwarf Mistletoe in Coastal British Columbia, Canada.
Sugimoto,
Y, Ueyama, T, and
Yasuda, N. In vitro
Production of Strigolactones by Plant Root Cultures.
Takagi,
K, Okazawa, A, Wada, Y,
Trakulnaleamsai, C,
Fukusaki, E, Yoneyama, K, Takeuchi, Y, and Kobayashi, APhotoresponse
Analysis
of Phytochrome A in the Non-photosynthetic Parasitic Plant; Orobanche
minor
Sm.
Tennakoon, KU, Bolin, JF, and Musselman, LJ. Structural and Functional Attributes of the Hypogeous Root Holoparasite Hydnora triceps Drege & Meyer (Hydnoraceae).
Stefanovic,
S, and Costea, M. Reticulate Evolution in the Parasitic Genus Cuscuta
(Dodders; Convolvulaceae).
Tennakoon,
KU. Potential of
Establishing Root
Hemiparasitic Sandalwood (Santalum album
L.) as a NTF Species in
the Buffer Zones of Forests and Degraded Lands in Australasia: a Sri
Lankan
Experience.
Thorogood,
CJ, Rumsey, FJ, and
Hiscock, SJ. Speciation
and Host Specificity in Orobanche.
Timko,
MP,Gowda, BS, Li, J, and
Lis, K, Deciphering
the Interaction of Striga with Hosts and Non-hosts.
Tomilov,
A, Tomilova, N,
Filappova, T, Gunathilake,
P, Wu, D-Y, Hoang, N, and Yoder, JI. Early Haustorium Development in Triphysaria:
A View from Inside the Nucleus.
van
der Kooij,TAW, Krupinska K,
and Krause, K. Characterization of the Tocochromanol Content and
Composition of Different
Species of the Parasitic Flowering Plant Genus Cuscuta.
Virupakshaiah,
DBM, Ameresh, SH,
and Mirji,
SB. Structure Analysis of Computer Generated Homologous Models of pm3
Protein in Triticum
aestivum
(Wheat).
Wegmann
K. 2000 Years of
Observation, Knowledge and
Research on Orobanche.
Williams,
AM, and Virtue, JG.
Calculation of Growing
Degree Days to Determine Optimum Timing of Herbicide Application for
Control of
Branched Broomrape Orobanche ramosa
in Pastures.
Xie,
X, Awad, AA, Yoneyama, K,
Sekimoto, H, Kusumoto,
D, Takeuchi, Y, Yoneyama, K. Qualitative and Quantitative Differences
of
Strigolactone Exudation Determine Host Specificity of Root Parasites Orobanche
and Striga.
Yoneyama,
K, Sekimoto, H,
Takeuchi, Y, and Yoneyama,
K. Nitrogen and Phosphorus Deficiencies Promote the Production and
Exudation of
5-Deoxystrigol in Sorghum.
Yonli,
D, Traoré, H,
Sérémé, P, Hess, DE, and
Sankara, P. Integrated Striga hermonthica Management Based Fusarium.
Yoshida,
S, and Shirasu, K.
Agrobacterium-Mediated
Transformation of Striga hermonthica.
A
Ahom, RI (1),
and Okereke, OU (2)
Varietal
Differences in Ability
of Sesame and Pigeon pea as Trap Crops to Induce Suicidal Seed
Germination in Striga
hermonthica
(Scrophulariaceae)
1.
Department of Crop and Environmental Protection, University of
Agriculture,
Makurdi, Benue State, Nigeria. Email: ie
2.
Department of Crop Science, University of Nigeria, Nsukka
Striga
hermonthica
is the most
serious constraint to
maize production in West Africa Savannah. Seventeen (17) varieties of
sesame
and 13 accessions of pigeon pea were evaluated for their ability to
stimulate Striga seed
germination in vitro using cut-root
technique. The test
crop varieties evaluated showed significant differences in their
ability to
stimulate seed germination in S. hermonthica. On the basis
of the results, the
trap crops varieties were grouped into five with respect to stimulant
production, viz., very high, high, moderate, low and very low. For
Sesame: Very
high (none), high (69B and Yandev _ 55) moderate (Ex-Pankshin-98,
73A-79B,
Cross-95, E-8, Ncriben-01M, 73A-H2B, 60-2-3-1-8B and Ciano-16), Low
(Yandev-75,
Type-4, Ciano _ 27, Eva and 69-1-1) and very low (Pachequeno and
Ncriben-03L).
For Pigeon pea: very high (TCC1035, Cita 4, TCC6, TCC8126, Cita 3, TCC
87 and
Cita 2), high (TCC2, TCC 8127, TCC 151, and Cita 1), and moderate (TCC8
and TCC
8129). The use of trap crops, which stimulate suicidal seed germination
in Striga fits into the
cultural practices of
the small - scale farmer in Nigeria. The traps crops used in this study
are
cash crops and commonly grown in Benue State - Nigeria. However,
varietal
differences exist between and within trap crops. The varieties of
sesame and
pigeon pea belonging to the very high and high stimulants production
groups are
therefore recommended for use by farmers in Nigeria to clean up or
reduce the
reserve of Striga
seeds in the soil.
Alers-Garcia, J
(1), Lewis, KC (1),
and Wright, LJ (1)
Parasite
Mediated Maternal
Effects in Bitter and Sweet Lupins
1.
Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge,
Massachusetts, 02142, USA. E-mails:
alers-garcia[at]rowland.harvard.edu, lewis[at]rowland.harvard.edu,
wright[at]rowland.harvard.edu.
A strong emphasis has been placed in the study of parasitic plants in forestry and agricultural settings given the potential for economic losses these "pests" have in their hosts via marked changes in growth, allometry and in many cases total crop failure. Most studies have overlooked the fact that parasitic plants can directly affect the growth environment of the maternal parent and thereby the development, size, viability and chemical composition of its progeny. Our research focuses on environmentally-mediated maternal effects of Castilleja indivisa, a hemiparasite, on high and low alkaloid content isogenic lines of Lupinus albus. We are particularly interested in examining the role and mechanisms by which the parasite affects host nutritional content and its implications in plant defense and reproduction. Castilleja indivisa is known to alter nutrient availability and allocation patterns of its hosts. Castilleja preferential uptake of N from its hosts is expected to result in a reduction in growth rate of host sinks (flowers and fruits) and seed provisioning (i.e. quality). Parasitized hosts are predicted to have lower seed size and greater seed C: N ratios than unparasitized hosts. However, since the intensity of parasitism is usually correlated with host N content, we predict a greater magnitude of maternal effects on high alkaloid hosts compare to low alkaloid hosts.
Alers-Garcia, J
(1), and Bever, JD
(2)
Size
Dependent Parasitism of Cuscuta
gronovii:
Its Implications on Host Population Size Structure and Dynamics
1.
Rowland Institute at Harvard, 100 Edwin H. Land Blvd., Cambridge,
Massachusetts, 02142, USA. E-mail:
alers-garcia[at]rowland.harvard.edu.
2.
Department of Biology, Indiana University, 1001 East Third St.,
Bloomington,
Indiana 47405-3700, USA. E-mail:
jbever[at]indiana.edu.
Parasitic
plants can have negative
effects on the fitness of their hosts. However less is known of how
parasitic
plants affect the population properties of their host plants. Our research focuses on
the genus Cuscuta (dodder), a
holoparasitic plant
that exhibits active host choice.
We particularly examined: 1) the effects of parasitism by Cuscuta
gronovii
on mean
population performance and size structure of its host Pilea
pumila,
2) the
mechanisms underlying
active host choice in dodder, and 3) the relationship between size
dependent
selection and length of the parasitic association on the interactions
of
individuals within a population. The results of our experiments show
that size
dependent parasitism and compensation at the population level are the
mechanisms underlying the increase of size inequality on parasitized
plant
populations. Dodder selectively establishes on the tallest individuals,
suppresses their growth and continues to spread onto unparasitized
plants that
have become taller. Dodder
is able
to discriminate among potential hosts and choose the tallest ones
within the
population at least fifteen days prior to parasitism. The effects of
dodder on
host individuals are dependent on the length of parasitism; dodder
causes a drastic
reduction on vegetative and reproductive parameters on early attacked
hosts
compared to those attacked later.
Under the studied scenario as well as in situations on
which host plant
size exhibits a positive correlation with competitive dominance,
parasite
foraging behavior as well as the responses of unparasitized individuals
are
crucial in understanding and predicting the outcome of parasitism in
population
plant properties.
Aly, R (1),
Shomin, H (1), Joel, DM
(1), Steinitz, B (2), Zelcer, A (2), and Gal-On, A (1)
A New
Approach to Parasitic Weed
Control Based on Silencing of a Key Metabolic Gene in the Parasite
1.
Department of Plant Pathology, Virology and Weed
Research, ARO, Newe-Yaar Research Center, P.O.Box 1021,
Ramat Yeshai 30095, Israel. E-mail:
radi[at]volcani.agri.gov.il,
shominh[at]gmail.com, dmjoel[at]volcani.agri.gov.il, amit[at]volcani.agri.gov.il
2.
Department of Plant Genetics, ARO, The Volcani Center, Israel. E-mail:
steintz[at]volcani.agri.gov.il, zelcer[at]volcani.agri.gov.il
The silencing approach has already been demonstrated as an effective control method against various pathogens. Gene silencing provides plants with defense against various pathogens, and is a tool of immense importance for research on plant development. The introduction of double-stranded RNA (dsRNA) proved to be a powerful tool for suppressing gene expression through a process known as post-transcriptional gene silencing in plants. In our study we used the inverted repeat technique for gene silencing of Mannose 6-phosphate reductase (M6PR), a key-gene in Orobanche spp. in order to provide the host plant with resistance against the parasite. A gene construct fusing the key gene for silencing to the binary vector (pBin-19) was already transformed to tobacco and tomato host plants. By PCR and RT-PCR analysis, transgenic plants were proved to have a specific PCR fragment (286 bp) which was designated on the mRNA of the O. aegyptiaca M6PR for silencing. Our results indicated that in-vitro production of small interfering RNAs (siRNAs) by introducing short double-stranded RNA molecules of the M6PR gene into O. aegyptiaca tubercles grown on tomato plants, facilitate suppression and degradation of the native M6PR mRNA, thereby reduction of total soluble solids (sugars) in the treated tubercles. Real-Time RT-PCR analysis showed that the endogenous M6PR mRNA of O. aegyptiaca tubercles or shoots grown on transgenic tomato plants harboring the M6PR silencing construct were reduced by 60-80% compared with the control (O. aegyptiaca grown on non-transgenic plants).
Aouali, S (1),
Bouznad, Z (2),
Zermane, N (2), El Khishine, D (3), Madkour, M (3), Faied, M (3),
Chaabane, M
(3)
Genetic
Diversity Among Orobanche
crenata
Ecotypes Revealed by RAPD and AFLPs Markers, in Algeria
1.
Institut Technique des Grandes Cultures, 1, rue
Pasteur, Hassan-Badi BP16-El-Harrach- Alger-Algérie. E-mail:
saouali[at]yahoo.fr
2.
Institut National Agronomique,
El-Harrach-Alger-Algérie. E-mail: bouznad[at]wissal.dz;
nzermane[at]hotmail.com
3.
Agricultural Engineering Research Institute (AGERI)-Cairo-Egypt. E-mail:
el_khishin_dina[at]hotmail.com; m.madkour[at]cgiar.org;
solygene[at]yahoo.com
The objectives of this study were to investigate the efficiency of RAPD and AFLP marker systems in detecting intraspecific genetic polymorphism, and to determine the level of diversity among six O. crenata ecotypes, from different geographical localities of El Mitidja. Ten decamer RAPD primers and, three AFLP primer combinations (EcRI/MseI), generated a total of 144 and 429 markers respectively. Dice's similarity matrices were prepared and used for analysis. The diversity index, effective multiplex ratio, and marker index values were higher for the AFLP. This technique appears to be more useful than RAPD in the analysis of limited genetic diversity among the 6 ecotypes of O. crenata tested. Both marker systems were able to discriminate among materials analyzed, but clear distinction between all ecotypes was obtained with AFLP markers. AFLP is therefore another tool for assessing genetic relationships among O. crenata ecotypes along with RAPD. The study, showed a proportional increase in genetic distance with geographical distance, when going from the center of El Mitidja to the eastern-center and the western-center respectively. It is probable that the dissemination center of this parasitic plant is the center of El Mitidja.
B
Bewick, TA.
(1), and Cascino, J (2)
Development
of a Biological
Herbicide for Control of Cuscuta spp.
1. U.S.
Department of Agriculture,
Mailstop 2220, Washington, D.C. 20250
2. Sylvan
Bioproducts, Inc, 198
Nolte Drive, Kittanning, Pennsylvania 16201
On May 18, 2005 the U.S. Environmental Protection Agency published a regulation that established an exemption from the requirement of a tolerance for residues of the microbial pesticide Alternaria destruens Strain 059, marketed commercially as Smolder_, on all agricultural commodities when applied and used in accordance with label directions for the control of dodder. This represented the culmination of 20 years of research but the beginning of efforts at commercial development. Large scale demonstrations were conducted in 2006 in several states in the U.S. with both a granular and a wetable powder formulation. Success was mixed. In Wisconsin cranberry fields, dodder control ranged from 52 to 100 per cent. In Massachusetts cranberry fields, dodder control ranged from 20 to 60 per cent. In Iowa carrot fields, dodder control ranged from 0 to 100 per cent. Differences in climatic conditions and, possibly, the genetic makeup of the dodder populations tested could account for this variability.
Bolin, JF (1),
Tennakoon, KU (2),
and Musselman, LJ (1)
Stable
Isotope and Nutrient
Relationships of the Root Holoparasite Hydnora
(Hydnoraceae) in Southern Africa
1.
Department of Biology, Old Dominion University,
Norfolk, VA 23529, USA. E-mail:
jbolin[at]odu.edu,
lmusselm[at]odu.edu
2.
Department of Botany, University of Peradeniya,
Peradeniya 20400, Sri Lanka. E-mail:
kushant[at]pdn.ac.lk
Hydnora is a genus of unusual plant parasites with a mainly African distribution. Most species of Hydnora reside underground and all lack stomata and leaves. Estimated transdermal water loss in Hydnora africana and Hydnora triceps rhizomes was 0.14_.02 and 0.19_.02 mg cm-1 hr-1, respectively. Due to its extremely water conservative nature Hydnora may be a useful model for parasite-host uptake. We measured carbon and nitrogen natural abundance stable isotope ratios for 11 Hydnora-host associations in southern Africa, including host plants with dominantly CAM or C3 metabolism. Hydnora-host isotope ratios were compared to 12 mistletoe-host associations, emphasizing relationships between host plants shared by Hydnora and mistletoes including Tapinanthus and Viscum species. Carbon and nitrogen isotope values for Hydnora are negatively correlated and carbon isotope ratios mirrored the host photosynthetic metabolism. For the first time we report mineral nutrition relationships for three holoparasite-CAM host associations. Total P and K levels were significantly elevated in the holoparasite relative to the host in most associations. Total Ca, Cl, Mg, N, Na, and S levels were significantly lower in the host.
Bouwmeester, HJ
(1,2), Cardoso, C
(1), Zhongkui, S (2), Matusova, R (1,2), Lopez-Raez, JA (2),
Charnikhova, T
(1), Verstappen, FWA (1,2), Rochange, S (3), Bécard, G (3) and
Ruyter-Spira, C (1)
Strigolactones,
Signals for
Friends and Enemies
1.
Laboratory for Plant Physiology, Wageningen University, Arboretumlaan
4, 6703
BD Wageningen, The
Netherlands. E-mail:
harro.bouwmeester[at]wur.nl; catarina.cardoso[at]wur.nl;
radoslava.matusova[at]wur.nl;
tatsiana.charnikhova[at]wur.nl; francel.verstappen[at]wur.nl;
carolien.ruyter-spira[at]wur.nl
2.
Plant Research International, P.O. Box 16, 6700 AA
Wageningen, The Netherlands. E-mail:
sun.zhongkui[at]wur.nl; juan.lopez-raez[at]wur.nl
3.
UMR 5546 CNRS/Université Paul Sabatier, 24,
chemin de Borde-Rouge, BP 42617, Auzeville 31326, Castanet-Tolosan,
France. E-mail:
rochange[at]scsv.ups-tlse.fr; becard[at]scsv.ups-tlse.fr
The strigolactones are signaling molecules that are used by the root parasitic broomrapes (Orobanche spp) and witchweeds (Striga spp) as well as the symbiotic arbuscular mycorrhizal (AM) fungi to detect the presence of their plant host. The requirements for such signaling molecules are that these compounds should be specifically indicative of the presence of a plant host. We are elucidating the biosynthetic origin of the strigolactones in several host plants of AM fungi as well as parasitic plants. This led to the discovery that the strigolactones are derived from the carotenoids - and should therefore be called apocarotenoids and not sesquiterpene lactones - and as such are quite "plant-specific". Considering the dual signaling role of the strigolactones it is interesting that there is an interaction between AM fungi and parasitic plants through the host plant, resulting in reduced parasitism by Striga hermonthica on sorghum and maize that are colonized by AM fungi. We will discuss the evidence that this interaction is mediated through the production of strigolactones. Also the further elucidation of the strigolactone biosynthetic pathway, initially focusing on the first dedicated step that is probably catalyzed by a carotenoid cleavage dioxygenase will be discussed. We are cloning genes from the pathway to make transgenic plants with altered strigolactone biosynthesis. These plants will be a great tool to study the importance of these signaling molecules for the interaction of plants with friends as well as enemies.
C
Cameron, DD
(1), Keith, AM (2), and
Seel, WE (3)
Rhinanthus
minor
as an
Ecosystem Engineer:
Understanding the Mechanistic Basis of Parasitic Plant-Induced Changes
in
Community Structure.
1.
Department of Animal and Plant Sciences, University of Sheffield, UK.
E-mail:
d.cameron[at]shef.ac.uk
2.
Centre for Ecology and Hydrology - Banchory, UK
3.
School of Biological Sciences, University of Aberdeen, UK
The root hemiparasite Rhinanthus minor, can suppress the abundance of grasses whilst promoting forbs in grassland communities, however, the outcome of its introduction is highly variable. We investigated the factors influencing this variability by studying the mechanisms through which the parasite acts to facilitate changes in community structure. Field manipulations confirmed that R. minor, suppresses the growth of grasses and whilst promoting that of forbs in the first growing season of a newly sown meadow. In contrast the removal of R. minor from mature meadow plots did not influence their floristic composition. In pot-based studies the parasite was highly damaging to grasses but had no significant effect on forbs although it did attach to them. Moreover, the parasite performed worst in terms of growth and photosynthesis when attached to forbs, even compared with unattached individuals. We hypothesized that forbs express resistant to the parasite. Tracer experiments using 1N-nitrate supplied to the host confirmed this as the parasite abstracts more nutrients from grasses than from forbs. Histological studies established that all of the forbs possessed successful resistance mechanisms to haustorial penetration of host vascular tissues whilst no successful resistance was observed in the grasses. Two different resistance mechanisms were observed in the forbs; hypersensitive cell-death and host lignification at the host-parasite interface. Our results establish that differential host resistance underlies the community level effects of R. minor as forbs possess a resistance capacity that other potential hosts do not, consequently the parasite moderates intra-specific competition within grassland communities promoting forb abundance.
Castillejo,
MA (1), Maldonado, AM (1), Dumas-Gaudot, E (2), Pérez de
Luque, A (3),
Rubiales, D (3), and Jorr’n, J (1)
Differential
expression
proteomics to investigate responses and resistance to Orobanche
crenata in
legumes
1.
Department of Biochemistry and Molecular Biology, University of
Cordoba,
C—rdoba, Spain. E-mail (corresponding author):
bf1jonoj[at]uco.es
2. UMR
1088 INRA/CNRS/UB (Plant-Microbe Environment) INRA-CMSE, Dijon, Cedex,
France
3.
IAS-CSIC, Cordoba, Spain.
In order to
study the plant response
to parasitic plants and the molecular basis of the resistance we have
used a
proteomic approach. The root proteome of two accessions of the model
legume Medicago
truncatula and crop pea displaying
differences in
their resistance phenotype, in control as well as in infected plants
have been
compared. We report quantitative and qualitative differences in the
two-dimensional
gel electrophoresis (2-DE) maps of different plant genotypes and plant
subjected to different treatments (control, non-infected, and
infected).
Differential spots were successfully identified by peptide mass
fingerprinting
(PMF) following MALDI-TOF mass spectrometry. Many of the proteins
identified
that show significant differences between genotypes and after parasitic
infection belong to the functional category of photosynthesis and
energetic
metabolism, and defense and stress-related proteins. Data will be
presented and
discussed in terms of plant spp. and genotype common and differential
responses, as well as compared with those previously obtained by using
classical biochemical and transcriptomic approaches. Data have been
published
or submitted (Castillejo et al., 2004. Phytochemistry 65: 1817; Jorrin
et al.,
2006. Euphytica
147: 37; Rossignol et al., 2006. Proteomics 6:
5529; Rispail et al., 2007. New Phytologist 173: 703; Castillejo et
al., 2007. Plant
Physiology (submitted).
Chachalis,
D (1), and Murdoch, AJ (2)
Potential
Use of Nijmegen-1 and
Smoke Water Solutions to Deplete Orobanche ramosa Seed
Banks in Greece
1. National
Agricultural Research
Foundation (NAGREF), Plant Protection Institute of Volos, P.O. Box
1303,
Fitoko, Volos 38001, Greece.
2. Department
of Agriculture, The
University of Reading, Earley Gate, P.O. Box 237, Reading RG6 6AR, UK E-mail:
a.j.murdoch[at]reading.ac.uk
Laboratory and field experiments were conducted to study the effect of using stimulants to deplete Orobanche ramosa seed banks. Germination stimulants tested in the laboratory were Nijmegen-1 (NE-1: 10-4, 10-6, 10-8 and 10-10 mol/L) and two smoke water (SW) solutions, ("Seed Starter" from Australia and a comparable solution produced by burning hay in Greece) were studied. SW concentrations tested were 100, 10, 1, 0.1 and 0.01% v/v aqueous solutions. In the field experiment, five treatments (10-5, 10-6, 10-8 mol/L of NE-1 respectively, 1% v/v local SW, and 10-5 mol/L of NE-1+ 1% v/v local SW) were tested in a tobacco field. The field was initially uninfected with Orobanche and 500-1000 O. ramosa seeds were placed at marked locations to which tobacco plants were subsequently transplanted. The field site was kept moist for a week to allow the seeds to precondition after which the stimulant solutions were sprayed using a backpack sprayer at 93.5L/ha spray volume and 207 kPa of pressure. Plots were then kept moist for two weeks to allow seeds to germinate and die before transplanting tobacco to each location. Additionally, in each plot at least 100 seeds were placed in nylon mesh packets at 2.5 cm depth. These packets were exhumed and germination was recorded. The non-germinated seeds on exhumation were placed in Petri-dish (1wk, 23¼C) with distilled water for further estimation of germinability of seeds. In the laboratory, 10-6 mol/Litre NE-1 induced 38% germination as did the standard 10-6 mol/Litre GR24. Lower and higher NE-1 concentrations exhibited much lower germination, at levels similar to water control (4% germination). The local SW stimulated 78% germination at 1% v/v concentration, higher than the "Seed Starter" SW (52%). At high concentrations, both SW strongly inhibited (less than 13%) germination. The "Seed Starter" SW at more diluted concentrations (0.1 and 0.01% v/v) exhibited a gradual decline of germination (45, 32% germination, respectively). In contrast, the local SW showed a 48% germination even at the lowest concentration (0.01%). Depletion of O. ramosa seeds, as recorded in the exhumed seed packets, was well over 50% with the optimum local SW treatment compared to 38% with 10-6 mol/L NE-1. There was little difference between the other treatments (max. depletion 32%). Some caution should be exercised as germination was incomplete at the time of exhumation and was allowed to continue in petri dishes moistened with water. Germination of O. ramosa seeds in situ in the soil was ½ to 1/3 of the total seed germination. The use of smoke and smoke water to stimulate germination in both laboratory and field is well-known for a wide range of species although very little work has been carried out on parasitic weeds. The potential of smoke water to deplete the Orobanche soil seed bank is therefore interesting and the implications of smoke water and other stimulants such as NE-1 to deplete O. ramosa seed banks before transplanting susceptible crops will be discussed.
Chiang, MY (1),
Hsieh, YC (1), Yuan,
CI (1), and Lin, FY (1)
Cuscuta
Species in Taiwan: Molecular
Differentiation and Related Findings
1.
Taiwan Agricultural Chemicals and Toxic Substances Research Institute,
11 Kuang
Ming Road, Wufeng, Taichung, Taiwan 413. E-mail: Chiang
myc[at]tactri.gov.tw,
Hsieh ych[at]tactri.gov.tw, Yuan yci[at]tactri.gov.tw, Lin
mtlin[at]tactri.gov.tw
Cuscuta in Taiwan consists of mainly three taxa: C. japonica, C. japonica var. formosana, and C. campestris. C. japonica and C. japonica var. fomosana parasitize woody hosts of lowland and mountain areas, respectively. C. campastris is predominantly associated with herbaceous hosts of lowland habitats. Additionally, C. chinense and C. australis have been documented, but the former is rare and the later has been noted as mis-identification of C. campestris. We used different PCR methods to study samples collected from widespread areas. ISSR (Inter Simple Repeat) markers could clearly differentiated morphologically diversified taxa of Cuscuta. ITS (Internal Transcribed Spacer) data revealed that C. campestris from different sites were relatively homogenous with similarity higher than 98%. However, ITS sequences among populations of C. japonica or C. japonica var. formosana were abnormally variable (similarity could be lower than 80%) for the species level. Our further investigations on ITS led to interesting findings on possible DNA transfer between C. japonica complex and their hosts.
D
De Mol, M (1),
and Heller, A (1)
Sap
Flow from Host to Mistletoe:
an Anatomical Approach
1.
Institute of Botany, University of Hohenheim, Garbenstrasse 30, 70599
Stuttgart, Germany. E-mail: mdemol[at]uni-hohenheim.de,
heller[at]uni-hohenheim.de
The mistletoe Viscum album L. is a hemiparasitic flowering plant. It is (partially) carbon autotrophic, but obtains water and nutrients by tapping into the wood of the host. Classical light microscopical methods and high-resolution 3D X-ray computed tomography were used on poplar (Populus x canadensis Moench, Salicaceae) infected with mistletoe (Viscum album L., Viscaceae) to understand water flow and development of the endophytic system. Direct vessel-vessel connections at the interface host-mistletoe ensure mass water and nutrient transport to the parasite. Almost every host vessel bordering the mistletoe haustorium had a simple perforation that directly connected them with the xylary elements of the parasite. The presence of the parasite showed a high and well directed influence not only on the quantity of wood produced by the host (hypertrophy), but also on the grain of the host wood. The mistletoe seems to direct actively the sap flow of the host towards its haustoria. In this respect, dimensions and morphology of the haustoria and host-mistletoe interface are of significant importance. The broad parasite vessels near the interface transport the sap to xylary elements with a smaller diameter, which conduct the water towards the cortical strands and the aerial parts of the mistletoe. Could this transition to narrower xylem elements pose a significant resistance for water conduction?
dePamphilis, C
(1), McNeal, J (2),
and Zhang, Y (1)
Genome
Evolution in Parasitic
Plants: New
Genomes, Surprising
Findings
1.
Department of Biology,
Penn State
University, University Park, PA, 16802
2.
Department of Plant
Biology, University
of Georgia, Athens, GA, 30602
Although most species of flowering plants are free-living and fully photosynthetic about 1% of plant species are direct parasites of photosynthetic plants, and as a result lead partly to fully heterotrophic lifestyles. How parasitism originated and how their genomes evolve under dramatically altered evolutionary constraints are fundamental problems. Here we report on the sequences of plastid genomes from two Cuscuta and one Pholisma (Lennoaceae) species, and compare them to Epifagus (Orobanchaceae), collectively representing three independent heterotrophic lineages. These genomes show unexpected retention of photosynthetic genes and pathways in some entirely heterotrophic species and almost perfect parallel reduction in gene content in others. There is even the possibility that some non-photosynthetic plants have lost their plastid genomes entirely. While plastid and mitochondrial genomes are now focus of intensive study in parasitic plants, nuclear genomes of parasites remain relatively understudied due to their large size and complexity. Large-scale EST studies and gene sequencing of parasites and parasite-host interactions are now feasible targets for research. These will provide crucial data for understanding parasite biology and developing effective strategies for parasite control.
Dewaele, D (1),
Elsen, A (1), and
Obiudoh, CA (2)
A
Study of Biodiversity of
African Radopholus Similis In
Uganda.
1.
Department of Biosystems, Kasteelpark Arenberg 13 - Bus 02455, B - 3001
Heverlee, Katholic Universiteit, Leuven, Belgium.
E-mail:
dirk.dewaele[at]biw.kuleuven.be, annemie.elsen[at]biw.kuleuven.be
2.
Biology Department, University Gent, K.L. Ledeganckstraat 35, B-9000
Gent,
Belgium. E-mail: cobiudoh[at]yahoo.com
The main problem that nematologist are facing during screening for nematode resistance is the variability in the reproduction of different R. similis populations. Assessment of this variability will be highly useful to banana breeding programs for incorporating resistance to nematodes. The reproductive fitness of four Radopholus similis populations (Ikulwe, Sendusu, Mukono and Mbarara) were studied on carrot disc (in vitro) and on plantain cultivar (in vivo) Obino l Ewai, as a function of time, inoculum densities and its pathogenicity on plant. In the first experiment, the reproductive fitness of the isolates was followed during two, four, six and ten weeks after inoculation. There were significantly (p<0.05) differences in the reproductive fitness of R. similis populations from Uganda as an effect of time. Increase in time increases the final nematode population. The experiment to test the effect of different inoculum density with respect to the reproduction of these populations on the carrot discs shows no significant different in their rate of reproduction at 6 weeks after inoculation. Regarding reproduction and pathogenicity of R. similis on plants, no definite conclusion can be drawn from the result obtained.
de
Zélicourt, A (1), Letousey, P
(2), Thoiron, S (1), Montiel, G (1), Simier, P (1), and Delavault,
P (1)
Molecular
analysis of resistance
mechanisms to Orobanche cumana in
sunflower
1.
Université de Nantes, Nantes Atlantique
Universités, Laboratoire de Biologie et Pathologie
Végétales, EA1157, 2 rue de
la Houssini�re, BP 92208, Nantes, F-44000 France.
Axel.De-Julien-De-Zelicourt[at]univ-nantes.fr,
philippe.delavault[at]univ-nantes.fr
2.
Université de Reims, Laboratoire de Stress,
Défenses et Reproduction des Plantes, UFR Sciences, BP 1039,
Reims F-51687
Cedex 2, France
In sunflower,
resistance to Orobanche
cumana
is
characterized by a low number of parasite attachments and a confinement
of the
parasite in host tissues leading to its necrosis. To help understand
what are
the mechanisms governing such resistance, a molecular approach was
employed
during both early and late responses of susceptible (2603) and
resistant (LR1)
sunflowers infected by O. cumana. The
expression patterns of defense-related genes were
investigated. The resistant genotype exhibited a stronger overall
defense
response against O. cumana than the
susceptible one, involving preferentially marker
genes of JA and SA pathways. Among them, HaDef1 (defensin),
appeared to be
characteristic of the LR1 resistance. Plant defensins are small basic
peptides
of 5-10 kDa and most of them exhibit antifungal activity. In LR1, among
the
three defensin encoding cDNA identified, only HaDef1 presented a
preferential root
expression pattern and was induced upon infection by the root parasitic
plant O.
cumana
few days
before necrosis occurred. A 5.8 kDa recombinant peptide, Ha-DEF1, was
produced
in E. coli.
Investigation of in vitro antifungal activity of Ha-DEF1 showed a
strong growth
inhibition of Saccharomyces cerevisiae and a
morphogenetic activity on Alternaria
brassicicola
germ
tube development. Bioassays also revealed that Ha-DEF1 rapidly induced
cell
death at the radicle apex of Orobanche seedlings but
not of another parasitic plant, Striga
hermonthica,
nor of
Arabidopsis thaliana. These results
demonstrate for the
first time a lethal effect of defensins on plant cells. The putative
mode of
action of defensin in Orobanche cell death and
its possible involvement in sunflower
resistance will be discussed.
Dhanapal,
GN(1), Borg, SJ ter (2), and Struik, PC(3)
Integrated
Management of Broomrape in India
1. Department
of Agronomy,
University of Agricultural Sciences, GKVK Campus, Bangalore-560 065,
India.
E-mail: gndhanapal[at]yahoo.co.in
2.
Hamelakkerlaan, 11, 6703 EE,
Wageningen, The Netherlands. E-mail:
Siny.terBorg[at]staf.TON.WAU.NL
3. Plant
Sciences,Crop and Weed
Ecology, Wageningen Agricultural University, Haarweg 333, 6709 RZ,
Wageningen,
The Netherlands. E-mail: Paul.Struik[at]wur.nl
Bidi
tobacco is a non-Virginia tobacco, being cultivated in Nipani (India)
for the
45 years under rainfed conditions. In India, Orobanche cernua is the most
pernicious parasitic
weed in tobacco cultivation. The severity of broomrape problem is
increasing
because of mono-cropping of tobacco and hand weeding is the only
practice to
control it. Among different chemicals tested GR 24 induced 58%
germination of
broomrape seeds under laboratory conditions. The positive interaction
between
GR 24 (I.0 ppm) and the root exudates of few crops deserves further
attention.
In trap crop field experiment, sunhemp and greengram crops reduced
broomrape
population by 68% and increased tobacco yields by 45% at 90 days after
transplanting (DAT). Glyphosate and Imazaquin at 0.50 kg ai/ha and 0.01
kg
ai/ha, respectively, reduced the number and dry weight of broomrape
spikes.
However, we suggest the following integrated cultural and
chemical control
approaches to obtain higher tobacco yields and minimize broomrape
population in
the soil for tobacco areas in Nipani and areas of similar
conditions in
India: (1) Grow trap crops (sunhemp/greengram) in the early spring and
incorporate in situ at 45
days after sowing; (2) Transplant tobacco after 15-20 days;
(3) Take up general hand weeding within 45 DAT; (4) Apply glyphosate at
60 DAT
at 0.50 kg at ai/ha (or less); (5) Remove the remaining few broomrapes
spikes
by hands or apply plant oils to prevent seed formation. Also a cropping
system
with trap crop - short fallow - tobacco is an ideal practice to reduce
the
broomrape seed inoculumÕs potential in the soil.
Draie, R (1),
Pouvreau, JB (1), Véronési, C (1),
Théodet, C
(1), Thoiron, S (1), Delavault, P (1) and Simier, P (1)
The
Sucrose-Degrading Enzymes in Orobanche ramosa.
Characterization and
Involvement in Growth, Cell Wall Synthesis and Starch Accumulation.
1.
Université de Nantes,
Nantes-Atlantique Universités, Laboratoire de Biologie et
Pathologie Végétales,
EA 1157, UFR Sciences et Techniques, 2 rue de la Houssinire F44322
Nantes,
France. ridadraie[at]hotmail.com,
jean-bernard.pouvreau[at]univ-nantes.fr,
christophe.veronesi[at]univ-nantes.fr,
catherine.theodet[at]univ-nantes.fr,
severine.thoiron[at]univ-nantes.fr,
philippe.delavault[at]univ-nantes.fr,
philippe.simier[at]univ-nantes.fr.
O.
ramosa
is an obligate
parasite of major crops such as tobacco,
tomato, oil seed rape and hemp. It has been known for more than two
decades
that the host-derived sucrose supports parasite growth. Nevertheless,
sucrose
metabolism in the parasite remains to be elucidated. We have initiated
studies
aiming at characterizing the molecular components, such as cell wall
invertase
(CWI), vacuolar invertase (VI), neutral/alkaline invertase (NI) and
sucrose
synthase (SuSy), involved in sucrose mobilization in Orobanche
ramosa
growing on
tomato roots. Our first
data show that tubercles display an equilibrated VI / NI ratio while
this ratio
is stronger in the growing subterranean stems due to a specific
increase in VI
activity. This reflects the key role of this enzyme during sucrose
utilization
in the growing stem where cell expansion occurs through vacuolar hexose
and
mannitol accumulation. The VI enzyme was purified using affinity and
gel
filtration chromatography. Only one isoenzyme was detected in stems,
and the
native form shows a pI of 3.8 and a molecular mass of 98 7 kDa. Protein sequencing is
in
progress. CWI activity is constant to a basal level in tubercles and
stems. In
contrast, tubercles display a significant SuSy activity. Using
antibodies
raised against faba bean SuSy, we show that this enzyme is strongly
associated
to tracheids and amyloplasts contained in parenchyma cells. It suggests
that in
tubercles SuSy is involved in the sucrose mobilization required for
cell wall
polysaccharide synthesis in tracheids and for starch accumulation in
parenchyma
cells.
Dubé,
M-P (1), and Belzile, FJ (1)
Genetic
variability among five
races of Striga gesnerioides
(Willd.) Vatke detected by ISSR, AFLP and cpSSR
analysis.
1.
Departement de phytologie, Université Laval,
Québec City, QC G1K 7P4, Canada.
Striga
gesnerioides
(Willd.) Vatke
is an obligate root
parasite of several dicotyledonous species including cowpea (Vigna
unguiculata
(L.)
Walp.), an important legume crop of the semi-arid regions of West
Africa. Based
on host-parasite interactions in the field, various races of S.
gesnerioides
attacking
cowpea have been
identified. In this study, we investigated the genetic variability
within and
between 44 populations of five of the previously recognized races of
the
parasite present in West Africa. Three different types of molecular
markers
were used on up to 10 individuals from each population. ISSR
(inter-simple
sequence repeat) markers showed no genetic variability within
populations. The
variability between the populations was also extremely low and did not
allow
discrimination of the five races. A few populations were more closely
related
(notably two populations from Togo), but no geographical or "racial"
clustering
could be seen. Further work with ISSR and AFLP (amplified fragment
length
polymorphism) markers is in progress to improve the accuracy of the
analysis.
Finally, we used cpSSR (chloroplastic simple sequence repeat) markers
as these
have been shown, in many studies, to reveal greater amounts of
polymorphism at
the intraspecific level. A total of 34 cpSSR primer pairs from various
species
were used, 26 of which produced amplicons in Striga. Absolutely no
polymorphism
was observed with cpSSR markers emphasizing that despite a large
geographical
distribution, very low genetic variability can be found in the
different
populations of S. gesnerioides. This may be
due in part to the autogamous mode of
reproduction of the parasite.
Dunlavey, R
(1), Logan, BA (1) and
Reblin, JS (1)
The
Influence of Arceuthobium
pusillum
Infection on the Hydraulic Architecture of White Spruce Stems
1.
Department of Biology, Bowdoin College, Brunswick, ME 04011USA
E-mail:
rdunlave[at]bowdoin.edu, blogan[at]bowdoin.edu, jreblin[at]bowdoin.edu
Arceuthobium
pusillum
(eastern dwarf
mistletoe) is an
aerial hemiparasitic angiosperm whose primary hosts are white spruce (Picea
glauca),
red spruce
(Picea rubens)
and black spruce (Picea mariana).
Although the
biology, ecology, and population genetics of Arceuthobium species have
been examined in some
depth, comparatively less is known about the impacts of Arceuthobium infection on
the physiological
performance of their hosts. Arceuthobium infection is
characterized by the
establishment of an endophytic system that taps directly into host
xylem and
phloem, through which the parasite withdraws all of the water, mineral
nutrients and much of the fixed carbon that it needs to support its
growth. Along the
coast of Maine, Arceuthobium
pusillum
infection
causes severe mortality in white spruce stands.
We investigated the impact of Arceuthobium
pusillum
infection on
white spruce stem
hydraulic conductivity. Infection
reduced white spruce stemsÕ capacity to deliver water
(specific conductivity)
by more than 25%. This
perturbation may explain the dramatic reduction (>40%) in needle
size distal
to infection. Needle
size
reductions may offset reductions in hydraulic conductivity and water
use by Arceuthobium to restore the
balance between host
leaf area and the capacity to transport water through stems. As a result, infection had
no
significant impact on a stemÕs capacity to deliver water
when expressed on the
basis of leaf area distal to infection (leaf specific conductivity). Furthermore, we found that
infection
did not have an impact on the occurrence of cavitation in white spruce
stems.
Dzomeku,
IK (1),
and Murdoch, AJ (2)
Studies
on Seed Dormancy, Germination and Seedling Emergence of Striga
Hermonthica
1
Department of Agronomy, Faculty of Agriculture, University
of
Development Studies, P.O. Box TL 1882. Nyankpala, Tamale, Ghana.
2.
The
University of Reading, School of Agriculture, Seed Science Laboratory. P. O. Box 236. Reading UK.
This
paper
represents the first attempt to apply a conditioning model for
parasitic weeds
to seeds in soil in the glasshouse. The previous models developed for Striga hermonthica and for three Orobanche species were
only applied
empirically and were not validated on independent data sets. The
results
indicate that S. hermonthica seeds
recovered from eight soil environments of different
drought and urea treatments, attained germination within 14-28 days and
these
optimum periods were similar to predictions based on the in
vitro
model, Once
the seeds have been in
imbibed storage in the soil for more than about 28 days in this
experiment,
induction of secondary dormancy increased but gradually, leading to a
slow
decrease in germination over a period of 91 days which in most
environments did
not terminate in zero germination. After 119 days of conditioning in
the soil,
germination percentages remain significantly high compared to the model
predictions. The implication of the present findings for the control of
S.
hermonthica
was
discussed.
E
Echevarr’a-Zome–o,
S (1),
Pérez-de-Luque, A (2), Jorr’n, J (1), and
Maldonado, AM (1)
Histochemical
analysis of defense
responses involved in resistance of sunflower ( Helianthus
annuus)
to Orobanche
cumana
1.
Agricultural and Plant Biochemistry Research Group, Dpt. of
Biochemistry and
Molecular Biology, University of Cordoba. Cordoba, Spain, E-mail:
g72eczos[at]uco.es; bf1jonoj[at]uco.es; bb2maala[at]uco.es
2.
IFAPA-CICE (Junta de Andalucia), CIFA, çrea
de Mejora y Biotecnolog’a, C—rdoba, Spain.
E-mail:
bb2pelua[at]uco.es
Sunflower
broomrape (Orobanche
cumana Wallr.) is considered as
one of the
major constraints for sunflower production in Mediterranean areas1.
Breeding for resistance is regarded as the most effective and
environmental
friendly solution to control this parasite. However, the existing
sources of
genetic resistance are defeated by emergence of new more virulent races
of the
parasite.
In this work we
have analysed the
interaction between sunflower and O. cumana in order to
get insights into the
mechanisms involved in resistance. The interaction between O.
cumana and two sunflower
genotypes showing different behavior
against the race F of O. cumana, HE-39998
(susceptible) and HE-39999 (resistant), were
monitored by pot and Petri dish bioassays. Then, using histochemical
procedures
and microscopic observations, compatible and incompatible interactions
were
compared and several defense responses involved in resistance were
identified2.
Suberization and protein cross-linking at the cell wall were observed
in the
resistant sunflower cells in contact with the parasite, preventing
parasite
penetration and connection to the host vascular system. In addition,
fluorescence and confocal laser microscopy observations revealed
accumulation
of phenolic compounds during the incompatible interaction, which is in
agreement with these metabolites playing a defensive role during H.
annuus
- O.
cumana
interaction3.
1. Shindrova,
et al. (1998) Helia
21: 55.
2.
Echevarr’a-Zome–o, et al. (2006)
Journal of Experimental Botany, 57: 4189.
3. Serghini,
et
al. (2001) Journal
of Experimental Botany 52: 2227.
Eizenberg, H
(1), Ephrath, J (2),
Lande, T (1), Achdari, G (1), and Hershenhorn, J (1)
Temporal
Thermal and Special
Model for Orobanche
Management
1.
Agricultural Research Organization, Newe-Ya'ar Research Center, Ramat
Yishay,
Israel. eizenber[at]volcani.agri.gov.il
2.
Wyler Department of Dryland Agriculture, Jacob Blaustein Institutes for
Desert
Research, Sede-Boqer, Ben-Gurion University of the Negev, Israel.
The overall
goal of our study is to
develop a decision support system for Orobanche control base
on spatial and
temporal sub-models. a) Temporal model: in previous studies, a
mathematically
relations between temperature and the parasitism process of O.
aegyptiaca,
O.
minor
and O.
cumana,
in tomato,
red clover, and
sunflower, respectively, was shown. A Growing Degree Days (GDD) model
was developed
to predict Orobanche parasitism in
these crops. Using a sigmoid function allows us to
predict the timing of the various Orobanche spp.
developmental including
subsurface stages. Herbicidal control of Orobanche was achieved
in tomato, red clover,
and sunflower using ALS inhibitors. The most effective control was
achieved in
the subsurface parasitism phase. Optimized chemical control is achieved
when
minimal herbicide rates are applied to the host at the most susceptible
stage
of the parasite. Herbicide application timing is based on the GDD model
mentioned above. Recently, the option of in-situ monitoring
sub-surface parasitism
was introduced by using the minirhizotron camera. This is a
non-destructive
tool for detecting and monitoring parasitism over time. The
minirhizotron
technology is essential for verifying the herbicide rate models. This
will
allow making proper decisions regarding to herbicide application
timing. b)
Remote sensing approach was used for modeling the spatial distribution
of O.
aegyptiaca
in
tomato and in dill fields. IR, NIR and RGB aerial images were taken
from
satellite and from air for tomato and parsley fields infected with O.
aegyptiaca.
Orobanche
aegyptiaca
could be
partially detected only by RGB aerial images.
Elzein,
A
(1), Fen, B (2), Kroschel, J (3), Marley, P (4), and Cadisch, G (1)
Synergy
Between Striga- Mycoherbicides
"Fusarium oxysporum f.sp.
strigae" and
Resistant Cultivars Under
Field Conditions: Step Towards Integrated Striga
Control in Africa
1. Institute
for Plant production
and Agroecology in the Tropics and Subtropics (380), University of
Hohenheim,
D-70593, Stuttgart, Germany. Email: gasim[at]uni-hohenheim.de,
cadisch[at]uni-hohenheim.de.
2.
International Institute of
Tropical Agriculture (IITA), 08 BP 0932 Tri Postal, Cotonou, Republic
of Benin.
E-mail: f.beed[at]iita-uganda.org.
3. Integrated
Crop Management
Division, International Potato Center (CIP), Av. La
Molina 1895,
Apartado 1558, Lima 12, Peru. E-mail: j.kroschel[at]cgiar.org.
4. Department
of Crop Protection,
Faculty of Agriculture/Institute for Agricultural Research, Ahmadu
Bello
University, Samaru, Zaria, Nigeria. E-mail: psmarley[at]yahoo.co.uk.
Striga spp. are
important constraints in
cereal and legume production in semi-arid tropical Africa. An
integrated
approach, in which biocontrol represents an important component,
appears to be
a promising strategy for reducing Striga infestation. Fusarium
oxysporum
f.sp. strigae (isolates Foxy
2 & PSM197) are
potential, highly host specific mycoherbicides against S.
hermonthica.
For
facilitating practical field
application, our recent research focuses on the development of
appropriate mycoherbicidal
formulations and delivery systems. Hence, Pesta formulation made by
encapsulating fungal inoculum in a matrix composed of durum
wheat-flour,
kaolin, and sucrose, was developed. Seed treatment technology for
coating
sorghum and maize seeds as an attractive option for further minimizing
the
inoculum amount and facilitating delivery of Striga-mycoherbicides
was also provided.
Integration of Pesta formulation and treated seeds containing Striga-mycoherbicides
(Foxy 2 &
PSM197) with Striga resistant and
susceptible maize and sorghum cultivars under field
conditions of West Africa was investigated. The combination Pesta
granules or
treated seeds and resistant maize and sorghum cultivars enhanced
clearly both
mycoherbicides efficacy, and showed the strongest suppressive effect on
Striga
compared
to
susceptible cultivars. The difference between the resistant and the
susceptible
cultivars was stronger for maize than for sorghum. On average (i.e. the
average
effect of both isolates), they reduced the number of emerged Striga plants per
plot by 96% or 89% when
the two isolates formulated as Pesta granules or delivered as coated
seeds,
respectively, and combined with the resistant maize cultivars compared
with the
control of the susceptible cultivars. On the other hand, the respective
reductions when the two isolates integrated with the susceptible maize
cultivars were 85 %, and 21%. Improvement in maize and sorghum
performances (height, grain yield, stalks dry weight, etc.) was
recorded.
Further, both mycoherbicides maintained excellent viability
(shelf-life) on
Pesta products and treated seeds after one year of storage which would
be
sufficient for their use under practical conditions of storage,
handling and
delivery. The suitability of Pesta and seed treatment technology for
formulating and delivering Striga-mycoherbicides
and their compatibility and synergy with Striga resistant
cultivars, are highly
relevant to the realization of an integrated Striga control
approach adoptable and
applicable by subsistence farmers in Africa.
Key
words:
Weed
biological
control,
Mycoherbicide,
Encapsulation,
Seed coating,
Integrated control, Fusarium
oxysporum, Striga
hermonthica, Striga-resistant
cultivars, Sorghum bicolor, Zea mays
Elzein,
A
(1), Kroschel, J (2), Fen, B (3), Marley, P (4), and Cadisch, G (1)
Compatibility
of Striga-Mycoherbicides
with Fungicides
Delivered Using Seed Treatment Technology and its Implication For Striga and
Cereal Fungal Diseases
Control
1. Institute
for Plant production
and Agroecology in the Tropics and Subtropics (380), University of
Hohenheim,
D-70593, Stuttgart, Germany E-mail: gasim[at]uni-hohenheim.de,
cadisch[at]uni-hohenheim.de.
2. Integrated
Crop Management
Division, International Potato Center (CIP), Av. La
Molina 1895,
Apartado 1558, Lima 12, Peru. Email: j.kroschel[at]cgiar.org).
3.
International Institute of
Tropical Agriculture (IITA), 08 BP 0932 Tri Postal, Cotonou,Republic of
Benin.
E-mail: f.beed[at]iita-uganda.org.
4. Department
of Crop Protection,
Faculty of Agriculture/Institute for Agricultural Research, Ahmadu
Bello
University, Samaru, Zaria, Nigeria. E-mail: psmarley[at]yahoo.co.uk.
Root parasitic
weeds of the genus Striga and fungal
diseases constitute a
major biotic constraint to staple food production in Africa, and
consequently
aggravate hunger and poverty. With the aim of improving sorghum and
maize
performance and yield, an investigation on the possibility of
delivering the
potential Striga-mycoherbicides
(Foxy 2 & PSM197) and some selected fungicides using seed
treatment
technology to control simultaneously Striga and sorghum
and maize fungal
diseases was made for the first time. Sorghum film-coated seeds with
different
application rates (dosages) of Apron XL and Ridomil Gold in combination
with
the mycohericides Foxy 2 and PSM197 and different coating adhesives
were used.
The effects of Apron XL and Ridomil Gold fungicides on growth and
sporulation
of the two isolates was examined by growing the film-coated sorghum
seeds on
PDA media. Delivering of the fungicides Apron XL and Ridomil with Striga-mycoherbicides
Foxy 2 and PSM197
using seed treatment technology did not interfere with seed coating
process as
well as with the initial survival of fungal isolates on coated sorghum
seeds.
Apron XL clearly enhanced the growth, sporulation and viability of both
isolates, indicating strong compatibility with Striga-
mycoherbicides. However, Ridomil
Gold was not compatible on PDA medium. Under filed conditions of West
Africa,
the integration of fungicide Apron XL (at a rate of 0.5 ml /kg of
seeds) with Striga-mycoherbicides
(Foxy2 & PSM197)
and resistant maize cultivars using seed treatment technology and
Arabic gum as
adhesive showed significant reduction in Striga emergence by
81% and 90% compared
to the respective resistant and susceptible controls. Improved
performance of
maize treated with Striga-mycoherbicides
and fungicide was recorded. The compatibility between Striga-mycoherbicides
and Apron XL
fungicide has significant implication for controlling simultaneously Striga and sorghum
and maize fungal
diseases and improving crops performance and yield.
F
Fan, ZW (1),
Buschmann, H (2), Shen,
YD (1), Lu, Y (1), and Sauerborn, J (2)
Induced
Host Resistance as a
Control Method for Parasitic Weeds
1.
Environment and Plant Protection Institute, Chinese Academy of Tropical
Agricultural Sciences; Key Laboratory for Pest Detection and Monitor of
Tropical Agriculture of Hainan Province, Hainan 571737, China
2.
Institute of Plant Production and Agroecology in the Tropics and
Subtropics,
University of Hohenheim, Stuttgart 70593, Germany
Parasitic weeds
restrict crop
production in many countries. Plant induced resistance is against not
only
pathogens and herbivores, but also parasitic weeds. Induced resistance
against
parasitic weeds has been demonstrated in the associations of sunflower-Orobanche
cumana,
tobacco/hemp-O. ramosa and pea-O.
crenata
under
greenhouse conditions and/or in the field. Plant
activators include biotic and abiotic agents. Host plants underlay
systemic
acquired resistance (SAR) or induced systemic resistance (ISR) pathway
against
parasitic weeds. Induced resistance should be integrated in the
parasitic weed
management systems. This paper reviews the history and development,
pathway and
mechanism, as well as prospect and outlook of plant induced resistance
on the
control of parasitic weeds.
Fernández-Aparicio,
M (1), Pérez-de-Luque, A (2), Sillero, JC (2) and Rubiales,
D (1)
Yield
increase in oat-faba bean
intercrops under heavy Orobanche crenata
infections.
1.
CSIC, Instituto de Agricultura Sostenible,
Apdo. 4084, 14080 C—rdoba, Spain. E-mail:
monfapru[at]yahoo.com,
ge2ruozd[at]uco.es
2.
IFAPA Centro "Alameda del Obispo", Apdo 3092,
14080 C—rdoba, Spain. E-mail: bb2pelua[at]uco.es,
josefa.sillero.ext[at]juntadeandalucia.es
Orobanche
crenata
(crenata
broomrape) causes severe
damage on legumes. Several cultural, biological, and chemical
strategies have
been suggested but none is completely successful or practicable in low
input
farming systems. We showed previously that broomrape infection on
legumes is
reduced in intercrops with oat. In the present experiment we studied
the effect
of broomrape reduction due to oat-faba bean intercrops on faba bean and
broomrape biological dry matter (BDM). The assay was conducted in an
infested
experimental field in C—rdoba, Spain in organic conditions.
Susceptible faba
bean cv. "Prothabon" was grown as sole crop and mixed with oat cv.
"Cory" in
50% replacement model intercrop. Crops were laid out on plots (1.5x8 m2)
in a complete randomized block design with three replicates. The high
Land
Equivalent Ratio value (LER=1.3) achieved shows that environmental
sources for
oat-faba bean growth are used on average 30% more efficiently in the
intercrops
than in the respective sole crops due to a) the degree of resource
complementarity of faba bean-oat system in absence of any fertilization
and b)
the reduction of crenata broomrape attached per faba bean plant due to
the
inhibitory effect of oat. Faba bean BDM was 928 g/m2
in sole crop
and 666 g/m2 in intercrop. Broomrape BDM was
reduced from 193 g/m2
to 42 g/m2 due to intercrop, reducing
proportionally the number of
seeds laid in soil.
Fernández-Aparicio,
M (1),
Pérez-de-Luque, A (2), and Rubiales, D (1)
Response
of Medicago
truncatula
Accessions to Various Species of Orobanche
1.
CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba,
Apdo. 4084, Spain.
monfapru[at]yahoo.com, ge2ruozd[at]uco.es.
2.
IFAPA-CICE, "Alameda del Obispo", 14080 C—rdoba, Apdo. 3092,
Spain.
bb2pelua[at]uco.es
There is
increasing interest in the
legume species Medicago truncatula as a model in
genomic studies. Genotypic variation for the
mechanisms of resistance was found between M. truncatula accessions
with an
accession highly resistant and another highly susceptible to O.
aegyptiaca,
O.
foetida
var broteri
and O. ramosa. Similar
variation, but in reverse,
was observed with O. nana. In
vitro
studies showed
that M. truncatula can induce
high levels of O.
aegyptiaca,
O.
foetida
var
broteri, O. nana,
O. minor and O.
ramosa
seed
germination, but rather low levels of O. cumana, O.
crinita
and O.
crenata.
Differences
in germination level
among accessions were highly significant. Accessions also significantly
varied
in the penetration response to O. aegyptiaca, O.
foetida
var broteri, O.
ramosa
and O.
nana.
Increasing
the germination level
on O. cumana, O.
aegyptiaca,
O.
ramosa
and O.
minor
through
applications of the synthetic germination stimulant GR24 did not result
in
increased infection. However, infection by O. nana increased
markedly in the resistant
accession. GR24 was no effective inducing germinating O.
crinita,
O.
foetida
var broteri
and O. foetida var foetida
seeds. The variation
observed for induction of germination of these species by M.
truncatula
and of
subsequent attachment will
be useful to isolating and characterising genes involved in early
stages of Orobanche - host plant
interaction and for
the study of the biosynthetic pathways of production for germination
stimulants.
Fernández-Aparicio,
M (1), Flores, F
(2), Pérez-de-Luque, A (3) and Rubiales, D (1)
Yield
losses in pea as a function
of Orobanche crenata
levels of infection.
1.
CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba,
Apdo. 4084, Spain
E-mail:
monfapru[at]yahoo.com,
ge2ruozd[at]uco.es
2.
Escuela Politécnica la Rábida, Universidad de
Huelva, 21819 Palos de la Frontera, Spain
E-mail:
fflores[at]uhu.es
3.
IFAPA Centro "Alameda del Obispo", Apdo 3092,
14080 C—rdoba, Spain
E-mail:
bb2pelua[at]uco.es
Reduction of
biomass and seed yield
and size were studied on pea (Pisum sativum L.) as a
function of level of
infection by crenata broomrape (Orobanche crenata Forsk). The
susceptible pea
cultivar "Messire" was sown in a distance between plants and rows of
0.5 meter
in a highly but no homogeneously naturally infested plot, what allowed
us to
study yield components in pea plants with a variable level of
infection,
ranging from 0 to 21 emerged broomrapes per pea plant. Pea productivity
was
measured as dry total biomass (DMp), seed yield
(SYp) and
number of seeds (NSp) measured per pea plant.
The infection level
was studied per pea plant determining the number of emerged broomrapes
(Nb)
and parasitic dry matter (DMb) measured at
harvest. The following
models were used for the prediction of productivity losses. Dry total
biomass
of pea was reduced with infection, as a function of number of emerged
broomrapes DMp = 8.66+15.04e-0.20*Nb
(r2=0.64),
or broomrape biomass, DMp = 8.38+16.23e-0.30*DMb
(r2=0.63).
Pea seed yield were influenced by the
infection level, both by number of broomrapes SYp
= -3.96 +
(103.86/(6.14+Nb)) (r2=0.73)
and broomrape biomass, SYp
= -3.20+13.74e-0.12*DMp (r2=0.67).
This reduced yield was
due to a decrease of number of seeds per pea plant NS p
=
-2.30+54.98e-0.14*Np (r2=0.70)
and NSp =
-17.49+70.30e-0.11*DMb (r2=0.66)),
whereas seed weight
was not influenced by infection level.
Funk,
H
(1), Berg, S (2), Krupinska, K (2), Maier, U (1) and Krause, K (2,3)
Complete
DNA Sequences of the
Plastid Genomes of Two Parasitic Flowering Plant Species, Cuscuta
reflexa and Cuscuta
gronovii
1.
Institute for Cell Biology, Philipps-University Marburg, 35032 Marburg,
Germany. E-mail:
helena.funk[at]staff.uni-marburg.de,
maier[at]staff.uni-marburg.de
2.
Institute of Botany, Plant Cell Biology,
Christian-Albrechts-University, 24098
Kiel, Germany.
E-mail:
kkrupinska[at]bot.uni-kiel.de
3.
Present address: Institute for Biology, University of Troms, 9037
Troms,
Norway.
E-mail:
kirsten.krause[at]ib.uit.no
We have
sequenced the complete
plastid chromosomes of two parasitic flowering plant species, Cuscuta
reflexa
and Cuscuta
gronovii.
Both
species are capable of performing photosynthesis, though with different
efficiencies. Together with the achlorophyllous E. virginiana, of which the
plastid genome was
already published over a decade ago, these species represent a
progression
series towards total dependency on the host plant. The plastid
chromosome sizes
were found to be larger than that of E. virginiana with 121.5 kbp
and 86.7 kbp,
respectively. Although the chromosome structure is similar to that of
non-parasitic plants, a number of insertions, deletions (indels) and
sequence
inversions were found. Gene losses are more pronounced in C.
gronovii
than in C.
reflexa,
encompassing
some photosynthetic
genes as well as many regulatory genes. Transcription of the C.
reflexa
ptDNA
resembles that of
nonparasitic higher plants regarding promoter structure and
transcription
patterns but shows marked differences in the steady state RNA profiles.
In C.
gronovii,
genes for
the photosynthetic apparatus were retained while the rpo genes coding
for the
plastid-encoded RNA polymerase that is responsible for their
transcription were
lost. Concomitantly, adaptations within the plastid genome have
occurred that
enable transcription mediated exclusively by a nuclear-encoded plastid
RNA
polymerase. Moreover, C. gronovii is the first
plant where a loss of the intron-encoded
splicing factor MatK was observed. Thus, Cuscuta is an
interesting model for the
evolution of reduced organellar genomes.
Gharib,
C(1), Haidar ,MA(1), Sleiman, FT(1) and Sidahmed, MM(1)
Germination
and Viability of Cuscuta
spp.
(Dodder) Seeds after Digestion in Sheep Rumen
1.
Faculty
of Agricultural and Food Sciences, American University of Beirut,
Lebanon. E-mail:
chadi.gharib[at]aub.edu.lb,
mhaidar[at]aub.edu.lb,
sleimanf[at]aub.edu.lb,
sidahmed[at]aub.edu.lb
Studies were
conducted to examine the
effect of sheep rumen digestion
on germination and viability of Cuscuta
spp. seeds in
comparison to non-parasitic weed seeds and two
crops (barley and lentil). Seed samples
were put in
small monofilament nylon bags and placed in the
plastic rumen of fistulated sheep for 1, 2, 3 and 4 days, respectively. Total percent germination
(Germination
+ viability) of seeds four days after placement (DAP) in the rumen were
85% for
Cuscuta
spp., 31% for Convolvulus
arvensis
and 17% for Chenopodium
album. Seeds
of Lolium
multiflorum
and Raphanus raphanistrum
died three DAP, while seeds of lentil and barley died one DAP. The results indicate that
grazing sheep
could be an important vector for carrying
viable weed seeds,
particularly Cuscuta
spp. seeds, in
their digestive system
and depositing them with their feces in un-infested fields.
G
Gebeyehu, S
(1), Belayneh, A (2) and
Tesfamariam, M (3)
Parasitic
Weeds in Ethiopia :
Challenges to Resource Poor and Small Scale Farmers
1.
Instiitut de recherche
pour le development,
IRD-Gene
Trop,911 Av. DÕAgropolis, BP 64501,F34394 Montpellier,
France. e-mail:
seyoum.gebeyehu[at]mpl.ird.fr
2.
Ambo Plant Protection Research Centre, P.O. Box 2003, Addis Ababa,
Ethiopia .
belay120[at]yahoo.com
3.
Institute for Plant Diseases, University of Bonn, Nussallee 9, D-53115
Bonn,
Germany tmekete[at]yahoo.com
Parasitic
weeds, Striga hermonthica on sorghum, S.
asiatica
on maize, cuscuta on noug, orobache on tomato and
faba bean, entailed
extensive loss of crop land productivity in the farmlands of drought
affected
and food deficit small scale farmers in Ethiopia. Reports indicate that
they
flourish in conditions that characterize the poorest farming community
(small
plots, monocropping, lack of oxen and natural manure and lack of
agricultural
inputs) and once areas are infested, they exacerbate the problem of
overall
poverty and food insecurity by decreasing yield. These and other
parasitic
weeds have been recorded and in general incur an estimated yield loss
of 5-100%
resulting in an escalating food aid. In this article, major parasitic
weeds of
economic importance and factors found to influence their expansion are
reviewed, their relationship with poverty is highlighted, control
measures and
a way forward to tackle the scourge of these weeds in crop production
is
suggested.
Goldwasser,
Y (1), Yoneyama, K (2), Xie, X (2), and
Yoneyama, K (2)
Identification
of the Stimulants Produced by Arabidopsis thaliana
Responsible for the Induction of
Orobanche
Seed Germination
1.
R.H.
Smith Institute of
Plant Sciences & Genetics in Agriculture, Faculty of
Agriculture, Food
& Environmental Sciences, The Hebrew University of Jerusalem,
Rehovot
76100, Israel
E-mail:
gold[at]agri.huji.ac.il
2.
Weed Science Center, Utsunomiya University, 350 Mine-machi,
Utsunomiya 321-8505, Japan.
E-mail:
yoneyama[at]cc.utsunomiya-u.ac.jp
The seeds of
obligate root parasitic
plants belonging to the Orobanchaceae require
specific conditions for
germination, including the unique requirement for induction by
stimulants
secreted by plant roots. In
recent years a group of
strigol-related natural stimulants from plant root exudates that induce
root
parasitic
plant seed germination have been identified
and termed as strigolactones. Strigolactones are abundant in plants
from a wide
range of botanical families, hosts and non-hosts of parasitic plants. In previous
studies we have
revealed that the model plant Arabidopsis thaliana induced
germination and is
susceptible to Orobanche aegyptiaca, Orobanche
ramosa
and Orobanche
minor.
The aim of
the present study was to produce,
extract, purify and analyze the strigolactone seed germination
stimulants
exuded by the roots of wild type A. thaliana that are
responsible for the
induction of Orobanche spp. seed
germination. To produce A. thaliana root exudates,
a novel hydroponics
culture system was developed and exudates were collected on activated
charcoal
placed in the culture growth medium. Exudates were extracted
from the activated charcoal with ethyl acetate and concentrated in
vacuo.
The crude extracts
were analyzed using high performance liquid chromatography connected to
tandem
mass spectrometry. All
chemical analyses were coupled with Orobanche spp. seed
germination bioassays.
The root exudates chemical analyses and accompanying bioassays revealed
several
strigolactones that are active in Orobanche
spp. seed
germination. Orobanchol was identified as a major Orobanche
spp. seed germination inducer produced by A. thaliana.
The final identification of other detected known and novel
strigolactones is in
progress.
Gunathilake, P
(1), Tomilov, A (1),
Tomilova, N (1), Fillapova, T (1) and Yoder, JI (1)
Macromolecular
Trafficking from
Host Plants into the Hemiparasitic Plant Triphysaria
versicolor
1.
Department of Plant Sciences, Mail Drop 3, University of
California-Davis,
Davis, California 95616-8780, USA
E-mail: jiyoder[at]ucdavis.edu
Cross family
transport of
informational macromolecules such as mRNA, proteins and microRNAs and
their
significance in parasitism is poorly understood. Understanding how
plants
synthesize, transform and respond to these molecules will further our
appreciation of host-parasite interactions and may lead to better
strategies
for vegetation management. However, a limitation has been the lack of
transformation and assay systems for macromolecular trafficking in
parasitic
plants. We developed both in vivo and in
vitro
assay systems
for studying macromolecule trafficking
between the root parasite Triphysaria versicolorr and its plant
hosts. Transgenic
roots were obtained on non-transgenic Triphysaria plants by Agrobacterium
rhizogenes
mediated
ex vitro root transformation. Transgenic roots were also obtained from
transformed calli. Micropropagated roots maintained their ability to
make
haustoria. Recent work showed that RNAi can traffic from a lettuce host
to in
vitro
cultured T.
versicolor
roots.
Transgenic GUSPlus T. versicolor root cultures
were attached to lettuce generating double
stranded RNA for GUS. Histochemical staining and semi-quantitative
RT-PCR
showed the silencing of GUS gene in root tips after haustoria
connection with
lettuce. In order to determine whether silencing signals are
translocated
throughout the parasitic plant, we made transgenic Arabidopsis bearing dsRNA
targeting the T.
versicolor
phytoene
desaturase gene (PDS). The hypothesis is that Triphysaria leaves will be
bleached when Triphysaria is attached to
Arabidopsis with the T.
versicolor
PDS construct,
but not when
attached non-transformed hosts.
The experiments to determine whether siRNA mediated gene
silencing of T.
versicolor
PDS
occurs via haustoria connection are underway and will be reported.
H
Haddad, A (1)
and Pala, M (1)
Significance
of Parasitic Weeds
for Food Legumes in Syria
1.
International Center for Agricultural
Research in the Dry Areas, (ICARDA), Aleppo, Syria.
E-mail:
a.haddad[at]cgiar.org, m.pala[at]cgiar.org
Parasitic
weeds, especially Orobanche and to a lesser
extent Cuscuta, have been
major constraints for
many crops in the Middle East, particularly legumes such as lentil,
faba bean,
and recently winter-sown chickpea.
Losses due to parasitic weeds are usually poorly
documented mainly due
to misleading survey results based on the observations of the parasite
in the
field rather than on the seed bank in the soil. Extensive research on
crop and
weed management in Syria, including crop rotations, fertilizers and
trap crops
as cultural control practices have had no impact on Orobanche alleviation.
Delayed planting date
is the only cultural practice available to the farmer to reduce Orobanche infestation,
but this practice also
reduces crop yield potential.
Breeding for Orobanche resistance has
had only limited success, except with
developed Egyptian faba bean varieties. Synthetic stimulants did not
perform in
vivo
as they did in
vitro
due to
calcareous soil, and did not either reduce the seed bank or the level
of
parasite infestation, Solar sterilization using second-hand plastic
sheets is
having an increasing role in reducing infestation levels of weeds,
including Orobanche, and other
pests, under greenhouse
vegetable production in extensive farming of coastal regions of Syria.
Chemical
control of parasitic weeds by herbicide application in some crops
appears
promising; however, more research is needed to minimize crop injury and
to
widen the herbicide selectivity for up-scaling recommendations to other
crops.
Despite available recommendations for chemical control of parasitic
weeds in
faba bean, and recently in lentils, adoption by farmers is low due to
lack of
effective extension. While much has
been learned about the evolution, physiology, genetics,
and ecology of parasitic plants in the past few decades, economic crop
losses
remain unacceptably high in most countries of the Mediterranean region.
Concerted efforts are needed to apply at farm level what is already
known about
parasitic weeds in food legumes.
Harrison, MJ (1)
The
Arbuscular Mycorrhizal
Symbiosis; Genomics Approaches to Dissect Development and Function
1.
Boyce Thompson Institute for Plant Research, Cornell University, Tower
Road,
Ithaca, NY, 14853, USA. email:mjh78[at]cornell.edu
In natural
ecosystems, most vascular
flowering plants live in symbiosis with arbuscular mycorrhizal (AM)
fungi.
These mutually beneficial associations develop in the roots, where the
fungus
colonizes the cortex to obtain carbon from the plant. In addition to
inhabiting
the root, the fungus establishes hyphal networks in the soil, via which
phosphorus and other mineral nutrients are transferred to the root.
Thus, the
symbiosis has a beneficial impact on plant health.
Fossil evidence suggests that plants have been associated
with AM fungi since they first colonized land and today, AM symbioses
are found
in ecosystems throughout the world.
Development of the AM symbiosis involves signal exchange
between the
symbionts and this occurs prior to, and following, the physical
interaction of
the symbionts. Once inside the root, both the fungal hyphae and plant
cells
differentiate to create a specialized symbiotic interface, the
arbuscule-cortical
cell interface, over which nutrients are exchanged. Recent studies
identified
strigolactones as one of the pre-contact signals in the AM symbiosis
indicating
an overlap with plant-parasitic plant interactions1.
It is possible
that there are parallels in the later stages of the interactions also.
We are using a
legume, Medicago
truncatula
and an
AM fungus, Glomus
versiforme, to
study the molecular events that underlie development and functioning of
the AM
symbiosis. By integrating transcriptional profiling information with
reverse
genetics approaches we have been able to identify plant genes whose
expression
is essential for the AM symbiosis.
1.
Akiyama, et al. (2005)
Nature 435: 824-827.
Heller, A (1),
Elzein, A (2), De
Mol, M (1), Kroschel, J (3) and Cadisch, G (2)
Colonization
of F. oxysporum f.sp.
strigae (Foxy
2) on roots of sorghum
plants and its implication for Striga
control using a seed treatment delivery system:
an anatomical study
1.
Institute of Botany (210), University of Hohenheim, D-70593, Stuttgart,
Germany
E-mail:
heller[at]uni-hohenheim, mdemol[at]uni-hohenheim.
2.
Institute for Plant production and Agroecology in the Tropics and
Subtropics
(380), University of Hohenheim, D-70593, Stuttgart, Germany
E-mail:
gasim[at]uni-hohenheim.de, cadisch[at]uni-hohenheim.de.
3.
Integrated Crop Management Division, International Potato Center (CIP),
Av. La
Molina 1895, Apartado 1558, Lima 12, Peru. E-mail:
j.kroschel[at]cgiar.org.
The application
of biocontrol agents
by a seed-coating procedure is an attractive option for establishing
the
biocontrol agent in the rhizosphere, the infection zone of the root
parasitic
weed Striga and
offers a simple delivery system. Fusarium oxysporum f.s. strigae (Foxy 2)
showed promising potential
in controlling Striga when applied
as a film-coat on sorghum seeds. The ability of Foxy 2 to
colonize the root system of sorghum seedlings that emerged from
film-coated
seeds, as a prerequisite, was proved by plating pieces of roots on PDA
medium.
In addition, anatomical investigations were performed to follow the
colonization of sorghum roots by Foxy 2. The spreading of the mycelia
were
observed by using light microscopy 1, 2, 3 and 4 weeks after
germination.
Transmission electron microscopy was used to get more information about
the
interaction between Foxy 2 and the roots of sorghum. Foxy 2 acts as a
pathogen
to Striga but is
non-pathogenic to other plants. Nevertheless, Foxy 2 was growing on the
root
surface and penetrating the roots of sorghum. Within 2 to 3 weeks it
was slowly
colonizing the whole cortical parenchyma of the root, but hyphae did
not enter
the vascular cylinder and kill the plants even after 4 weeks. On the
contrary,
Foxy 2 even seems to promote the growth of sorghum plants. This
indicates that
Foxy 2 met the criteria of being an effective mycoherbicide for
controlling S.
hermonthica
using
seed treatment technology.
Höniges,
A (1), Ardelean, A (1), and
Wegmann, K (1,2)
Ecological
and Physiological
Investigations on Orobanche
Species in the Spontaneous Flora of Romania
1.
Faculty of Natural Sciences, Vasile-Goldis-University Arad, Str.
Rebreanu nr.
91-93, RO-310414 Arad, Romania
2.
Center of Molecular Biology of Plants, University of Tuebingen, Auf der
Morgenstelle 5, D-72076 Tuebingen, Germany. E-mail:
a_hoeniges[at]yahoo.de
Wegmann[at]uvvg.ro
In contrast to
the few weedy species
most Orobanche
species have remained wild flowers in the spontaneous flora. We are
examining
the occurrence and distribution of non-weedy Orobanche species in
Romania, the soil
properties and climatic conditions required for conditioning Orobanche seeds and the
germination
stimulants exuded by host plants (e.g., low or sufficient germination
stimulants). The associated flora around each Orobanche spike was
recorded and root
exudates of the associated plants were tested for allelopathic effects
(e.g.,
germination inhibition or inhibition of radicle exoenzymes required for
penetrating into the host root). We are also testing possible reasons
for low
viable seed production or loss of seed by insects or fungi. The
obtained
results will be compared with the conditions in
Baden-WŸrttemberg, Southern
Germany, where most of the Romanian Orobanche species occur
also in limited
populations. The results will contribute to understanding the
ecosystems in
which non-weedy Orobanche species grow.
They may also provide information on the
conditions under which Orobanche species may
turn into weedy forms when ecological
conditions change. Moreover, they should provide a basis for fostering
rare Orobanche species in
Botanical Gardens for
the future. Methodological approaches and observations in Romania
during the
past two years will be presented.
K
Kaldenhoff, RWE
(1)
Molecular
Events During Cuscuta
Infection
1.
Darmstadt University of Technology, Applied Plant Science,
Schnittspahnstr. 10,
D-64287 Darmstadt, Germany
Dodder or Cuscutaceae are
holoparasitic plants subsisting
on other di- or monocotyledonous plant hosts. The infection process is
initiated by adherence of Cuscuta prehaustoria
to the host surface, followed by penetration
attempts of hyphae. For a better understanding of these processes, some
of the
genes expressed in host tissue or in the parasite were isolated and the
products characterized. For example, contact of Cuscuta
reflexa
prehaustoria
to tomato induced
expression of a plasma membrane bound cell wall localized
Arabinogalactan
protein (attAGP) in the host, right at the site of dodder attack. Using
RNAi-technique and targeted virus induced gene silencing, a correlation
of
attAGP expression level and the parasiteÕs attachment force
to host tomatoes
was observed. If the expression level of attAGP was reduced, C.
reflexa
attachment
capability was also
significantly reduced. C. reflexa infection
induced a signal in the host leading to
expression of tomato attAGP, which promotes the parasiteÕs
adherence. On the
other hand, Cuscuta expresses a
cysteine protease, which could be inhibited by an intrinsic
repressor. Circumvention of cysteine protease activity during an active
parasitic infestation by spraying an inhibitor solution on the plants,
leads to
reduced growth or death of Cuscuta and completely
heals the former host plant. Since the
inhibitor is a polypeptide, it is suggested to use it as a
biodegradable, non
toxic, Cuscuta
specific pesticide.
Kanampiu,
F
(1)
Striga
Weed Management Options under Smallholder Agriculture in Africa
1.
International Maize and Wheat
Improvement Center (CIMMYT), United Nations Avenue - Gigiri, P.O. Box
1041-00621, Nairobi, Kenya Email: f.kanampiu[at]cgiar.org
Agriculture is
the main source of livelihood for most
households in Africa. Damage caused to three most important crops,
maize,
sorghum and pearl millet by Striga spp. in Africa
is devastating to resource-challenged
farmers whose main source of livelihood can be threatened by complete
crop loss
to this root-parasitic weed. A range of effective component technology
control
practices focusing on factors such as hoe weeding and hand pulling; use
of
inorganic fertilizer and manure; crop rotations, fallowing, and early
planting;
use of Striga tolerant
varieties; soil fertility management and herbicides
have shown value in reducing losses - but these have been poorly
adopted and
have thus failed to slow the spread of Striga . New
technologies to deal with the
high levels of Striga in African
soils must meet four criteria to be widely adopted by
farmers: (1) have the ability to control Striga early
in its growing cycle in order to reduce yield loss; (2) deplete the Striga seed bank in
the soil; (3) be cost
effective; and (4) be compatible with existing cropping systems and
technologies. The most promising new Striga control
practice in maize is
coating seeds with resistance to ALS-inhibiting herbicides with
herbicides such
as imazapyr prior to planting. Extensive on-farm testing in several
African
countries has demonstrated the cost effectiveness of this technology.
It is
highly effective in reducing Striga incidence
two-fold - in terms of reduced seed bank in the
soil and decreased infection in maize. Integration with other control
options
and deployment of this technology offers medium-term solution for an
urgent
Striga problem
in
Africa until breeders identify sources of resistance for the long-term.
Kusumoto, D
(1), Yoneyama, K (1),
Yoneyama, K (1), Takeuchi, Y (1)
Induction
of Systemic Acquired
Resistance in Root Parasitic Weeds
1.
Weed Science Center, Utsunomiya University, 350 Mine-machi, Utsunomiya
321-8505, Japan. E=mail: kusumoto[at] cc.utsunomiya-u.ac.jp,
fragrance0917[at]yahoo.co.jp, yoneyama[at] cc.utsunomiya-u.ac.jp,
takeuchi[at]cc.utsunomiya-u.ac.jp
Induction of
resistance was studied
in red clover (Trifolium pratense) and rice (Oryza
sativa)
against root
parasitic weeds by
salicylic acid-mediated defenses.
Experiments on the resistance induction in red clover
against O.
minor
were carried
out as follows. The seeds of red clover and O. minor were sown in
pots packed with soil
and incubated from the end of November in a greenhouse.
Test chemicals were applied on the soil
surface. Three
months after incubation,
the number of the tubercles was decreased by the treatment with BTH and
tiadinil, inducers of SA-mediated defenses.
Red clover seedlings were grown for 4 weeks in Petri
dishes. The roots
were treated
with defense inducers for 3 hours.
The seeds of O. minor treated with
GR24 were sown on the roots of red
clover. After a
5-week incubation,
SA and BTH greatly reduced the number of the established parasites. The reduction was
attributable to the
development of haustoria before the radicle reached a host and the
activation
of defense responses in the host root including lignification of the
endodermis. Experiment on resistance induction in rice against Aeginetia
indica
were carried
out as follows. The seeds of rice (cv. Koshihikari) and Aeginetia
indica
were sown in
pots packed with
upland soil and tiadinil was applied to the soil surface. The pots were incubated in
a greenhouse
from the beginning of July. The
shoots of A. indica emerged from
the soil in late October in the non-treated pots. The
number, height, and weight of A. indica shoots were
decreased by the tiadinil treatment.
L
Lanini,
WT (1), Miranda, M (2), and Aouali, S (1)
Dodder
(Cuscuta pentagona)
Control in Roundup Ready
Alfalfa
1.
Department of Plant Sciences, Mail Stop 4, University of California,
One
Shields Avenue, Davis, California 95616, USA.
E-mail: wtlanini[at]ucdavis.edu, saouali[at]ucdavis.edu
2.
Department of Horticulture, 146A Plant Science Bldg., Cornell
University,
Ithaca, New York, 14853, USA.
E-mail: mrm67[at]cornell.edu
Dodder (Cuscuta
pentagona
and C.
indecora)
commonly
infests alfalfa, reducing
yield but also making it hard to dry after cutting.
In greenhouse experiments, dodder (C. pentagona) was allowed
to attach to Roundup
Ready (RR) alfalfa, and treated with glyphosate at 0.84 or 1.68 kg
ae/ha when
dodder stems were 15 to 20 cm in length.
Neither rate controlled dodder and dodder growth resumed
within a week
after treatment. Increasing
glyphosate rate to 3.36 kg ae/ha or sequential treatments of 1.68 kg
ae/ha made
at two week intervals, resulted in 99% control.
In a field study, dodder (C. pentagona) was allowed
to attach to RR
alfalfa. Glyphosate
(0.84 or 1.68
kg ae/ha) or imazethapyr (0.10 kg ai/ha) treatments were made when the
attached
dodder stems reached 10 to 20 cm in length, with subsequent treatments
applied
two weeks later. Dodder
control
with glyphosate treatments was greater than 90% regardless of rate,
while
imazethapyr treatments provided less than 50% control.
Imazethapyr treatment stunted the
dodder, but dodder growth resumed within a few weeks.
Following alfalfa harvest, dodder was observed to be
completely controlled on all glyphosate plots except those that
received a
single application of the low rate (0.84 kg ae/ha).
Although glyphosate effectively controlled dodder in the
field study, further field testing is being conducted to verify this
result,
since dodder easily survived glyphosate treatment in greenhouse
studies.
Lanini,
WT (1), Miranda, M (2), and Aouali, S (1)
Riches, CR (1),
and Mbwaga, AM (2)
Green
manure: A Striga
Management Technology Whose Time
Has Come?
1.
Natural Resources Institute, University of Greenwich, Chatham Maritime,
Kent,
ME4 4TB, UK. Email: Charlie[at]riches27.freeserve.co.uk
2.
Uyole Agricultural Research Institute, Mbeya, Tanzania. Email:
ambwaga[at]yahoo.co.uk
Soil fertility
depletion contributes
to low per capita food production and poverty in sub-Saharan Africa. An associated problem,
often indicative
soil fertility decline is increasing infestation of cereals by Striga
asiatica. Farmer participatory
research in Kyela
District and Matambo Division of the Ulugulu Mountains in Tanzania has
since
2000 identified low-cost approaches to increase agricultural
productivity on Striga
asiatica
infested
soils. Farmer
groups in four
villages in Kyela tested legume-cereal rotations and achieved average
upland
rice yield increases in 2003 and 2004 of 1114 (108%) and 827 kg ha-1
(72%)
respectively when planting after growing the green manure Crotalaria
ochroleuca
the
previous year and an additional 119 kg ha-1 (18%) when planting rice in
2004
after pigeon pea. Knowledge
of the
use of legume-rice rotations was disseminated to a further five
communities and
farmer-managed rice crops monitored in 2005 showed mean yield gains of
791
(74%) and 487 kg ha-1 (46%) when planted after Crotalaria or pigeon pea
compared to
continuous rice. Across
16 sites
in Matombo in 2005 mean maize yield was increased by 180 and 153%
following
Crotalaria and pigeon pea respectively.
Green manures are not new and there is a history of
limited adoption of
soil fertility technologies in sub-Saharan Africa. Understanding how
farmers
see soil fertility challenges, involving them in the selection of "best
bets"
and identifying the knowledge that farmers need to adopt new methods
successfully has been central to laying the foundations for up-scaling
adoption
of green manure on Striga infested land.
Liu, Y (1),
Liang, L (2) and Lynn DG
(1)
Gene
Regulation during Haustorial
Development and Shoot Initiation in Striga asiatica
1. Center
for Fundamental and Applied Molecular
Evolution, Departments of Chemistry and Biology, 1515
Dickey Dr. NE,
Emory University, Atlanta, GA 30322, USA.
E-mail:
yliu4[at]emory.edu, dlynn2[at]emory.edu
2.
University of Maryland Biotechnology Institute Center of Marine
Biotechnology
Suite 236, Columbus Center, 701 East Pratt Street, Baltimore, MD 21202,
USA.
E-mail: liangl[at]comb.umbi.umd.edu
In the
parasitic angiosperms the
vascular connection with the host occurs via formation of a specialized
organ
known as the haustorium. In Striga asiatica, a parasite of
grasses, haustorial
organogenesis is regulated by small molecules released from the host.
Methods
have now been developed for subtraction library screening of these
obligate
parasites. We now report the successful identification of two lignin
biosynthetic genes -- chorismate mutase (StCM1) and cinnamyl alcohol
dehydrogenase (StCAD1). The first StCM1 is the initial step in
phenylalanine,
tyrosine, and ultimately lignin biosynthesis, while the later StCAD1 is
the
last step in the formation of lignin monomers. The expression levels of
both
genes increases early in haustorial induction and remains elevated
throughout
organogenesis. The promoters of these two genes resulted in GUS
expression
specifically in the vascular tissue of Arabidopsis thaliana.
Over-expression of StCM1 resulted
in significant morphological changes, with the most remarkable change
being a
50% increase in the number of stem xylem bundles. We discuss the
possible
reasons for this significant alteration of the Arabidopsis
thaliana
development
program in the context
of haustorial development. Using the same approach, we induced shoot
initiation
of Striga Asiatica
by trans-zeatin, and constructed differential cDNA library to
characterize the
transcript profile that regulates shoot initiation.
Lozano-Baena,
MD (1), Lindsey, K
(2), Moreno MT (3), Rubiales, D (1), and
Pérez-de-Luque,
A (3)
Laser
Capture Microdissection
(LCM): New Technologies Apply to Study of the Parasitic Plant
Interactions
1.
CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba,
Apdo. 4084, Spain.
Lozano-Baena: b72lobam[at]uco.es, Rubiales: ge2ruozd[at]uco.es.
2.
School of Biological and Biomedical Sciences, University of Durham,
South Road,
Durham DH1 3LE, UK. Lindsey:
keith.lindsey[at]durham.ac.uk.
3.
IFAPA-CICE (Junta de Andaluc’a), Centro "Alameda del Obispo",
çrea de Mejora y Biotecnolog’a, Apdo. 3092, 14080
C—rdoba, Spain. Pérez-de-Luque:
bb2pelua[at]uco.es, Moreno:
mariat.moreno.yanguela[at]juntadeandalucia.es.
Using Laser
Capture Microdissection
(LCM) technique, individual cells can be isolated from tissue sections
for the
profiling of gene expression. For these reason, we have chosen this
method for
RNA extraction of cells from tissues of M. truncatula infected with O.
ramosa,
an important
parasitic plant pest
of legumes crops. We selected M. truncatula as a model
plant due to its
similarities with other legumes which have complex genomes to analyze.
Then we
could analyze the infection process and the defense mechanisms against
the attack
of this pathogen. Basically, the slide with tissue of interest is
placed under
an inverted microscope and the image is transferred to a computer
screen. A
film-coated cap is placed onto the tissue. We select cells of interest
and an
infrared laser is pulsed at the selected region and heat generated
determines
the melting of the thermoplastic film from the cap with the tissue in
correspondence to the demarcated region. Finally, the target region is
selectively pulled away from the surrounding tissues when the cap is
removed
and samples are collected in a tube, now ready for molecular analysis.
Other
authors have analyzed this interaction using the whole tissues with the
consequence being dilution of their RNA of interest in the total plant
RNA.
However, with this technique we attempted to analyze the transcriptome
of
target cells involved in the pathogenic process because we selected
only the
RNA of cell responding in this interaction.
Lozano-Baena,
MD (1), Moreno, MT
(2), Rubiales, D (1), and Pérez-de-Luque A (2)
Analyse
of Medicago truncatula
Resistance Against Orobanche
crenata
Using Citochemical Techniques
1.
CSIC, Instituto de Agricultura Sostenible, 14080 C—rdoba,
Apdo. 4084, Spain.
Lozano-Baena: b72lobam[at]uco.es, Rubiales: ge2ruozd[at]uco.es.
2.
IFAPA-CICE (Junta de Andaluc’a), Centro "Alameda del Obispo",
çrea de Mejora y Biotecnolog’a, Apdo. 3092, 14080
C—rdoba, Spain. Pérez-de-Luque:
bb2pelua[at]uco.es, Moreno:
mariat.moreno.yanguela[at]juntadeandalucia.es.
Medicago
truncatula
has emerged as
an important model
plant species for structural and functional genomics. The close
phylogenic
relationship of M. truncatula with crop
legumes (like faba bean, pea, vetches and lentil)
increases its value as a resource for understanding resistance against Orobanche spp. Orobanche
crenata
is a root
parasitic weed that
represents a major constraint for grain legume production in
Mediterranean and
West Asian countries. Different
cytological and histochemical methods (like stains, light and
fluorescence
microscopy, confocal studies, etc.) were used to study the mechanisms
of
resistance against O. crenata. For this
study we have chosen two accessions of M.
truncatula,
showing
early and late acting resistance. In the early resistance accession
(Mt196) we
found that the parasite died before a tubercle had formed. In the late
resistance accession (Mt53) the parasite became attached without
apparent
problems to the host roots but most of the established tubercles turned
dark
and died before emergence.
Lopez-Raez, JA
(1), Charnikhova, T
(1,2), Gomez-Roldan, V (3),
Matusova, R (1,2), de Vos, R (1), Schipper, B (1),
Verstappen, F (1,2),
Bino, R (1,2), Becard, G (3), and Bouwmeester, HJ (1,2)
The
Biosynthesis of the Tomato
Germination Stimulants is Promoted by Phosphate Starvation
1. Plant
Research International, P.O Box 16, 6700 AA
Wageningen, The Netherlands
2.
Laboratory for Plant Physiology, Wageningen University, Arboretumlaan
4, 6703
BD Wageningen, The Netherlands
3.
Laboratory for Cell Surfaces and Signalling in Plants, UMR 5546
Toulouse 3
University-CNRS, Catanet-Tolosan, France
Plants produce
a large variety of
secondary metabolites to defend themselves against harmful organisms
and to
attract others that are beneficial. One class of these important
signaling
compounds are the strigolactones which are secreted by plant roots in
extremely
low concentrations1. Strigolactones constitute a
group of secondary
metabolites produced by plants to attract symbiotic arbuscular
mycorrhizal (AM)
fungi under nutrient deficient conditions, inducing hyphal branching2.
However, at the same time they are used by the root parasitic
broomrapes (Orobanche spp) and
whitchweeds (Striga spp) to
germinate and complete
their life cycle3,4. Tomato (Solanum
lycopersicum
L.) is an
important fruit crop in
southern Europe, the Americas, the Middle East, and India, with
increasing
production in China, Japan, and Southeast Asia and their production is
highly
susceptible to infestation by Orobanche ramosa and Orobanche
aegyptiaca
that cause
severe yield losses up to
75%5. We focus on the biosynthetic origin of the
strigolactone
germination stimulants for O. ramosa and hyphal
branching factor for Gigaspora rosea by tomato cv.
MoneyMaker plants.
For this purpose both the inhibitor of carotenoids fluridone and tomato
mutants
were used and analyzed for their strigolactone production, and the
pivotal role
of these metabolites under nutrient deficient conditions will be
discussed. In
addition, we will show the progress of our research at the molecular
level in
the isolation and characterization of genes coding enzymes involved in
the
biosynthesis of the tomato strigolactones.
References
1.
Bouwmeester, H.J., et al. (2003) Current
Opinion in Plant Biology 6, 358-364
2. Akiyama,
K.,
et al. (2005) Nature
435, 824-827
3. Akiyama, K.,
and Hayashi, H.
(2006) Annals of Botany 97, 925-931
4.
Bouwmeester, H.J., et al. (2007) Trends
in Plant Science In press
5. Delavault,
P., and Thalouarn, P.
(2002). Gene 297, 85-92.
M
Matusova, R
(1,2), and Bouwmeester,
HJ (1,2)
The
Strigolactone Germination
Stimulants of the Plant-Parasitic Striga and Orobanche spp
are Derived from the
Carotenoid Pathway
1.
Plant Research International, P.O. Box 16, 6700 AA Wageningen, The
Netherlands.
2.
Laboratory for Plant Physiology, Wageningen University, Arboretumlaan
4, 6703
BD Wageningen, The Netherlands E-mail: Matusova
radoslava.matusova[at]wur.nl,
Bouwmeester harro.bouwmeester[at]wur.nl
The seeds of
the root-parasitic Striga and Orobanche spp
are only able to
germinate after induction by a chemical compound(s) exuded
from the
roots of their host. For
both Orobanche and Striga spp. several
germination stimulants
were identified from host and non-host plants.
In most cases, the compounds were shown to be isoprenoid
and
belong to one chemical class, collectively called the strigolactones. Strigolactones have been
detected in
many plant species showing that they are wide-spread in the plant
kingdom.
Because the germination stimulants are produced/exuded in extremely low
concentrations, an analytical approach to discover the biosynthetic
origin of
the germination stimulants is difficult. Therefore we used the high
sensitivity
of parasitic plant seeds to the germination stimulants and used a
germination
bioassay-guided approach to unravel the biosynthetic pathway. To assess the involvement
of the
isoprenoid biosynthetic pathways we investigated the induction of Striga hermonthica seed
germination by root exudates
of maize seedlings treated with inhibitors and of a series of maize
mutants. We
also used these inhibitors on cowpea (Vigna unguiculata) and sorghum (Sorghum
bicolor)
and assessed
the effects on the
root exudate-induced germination of S. hermonthica and Orobanche
crenata.
Our results
demonstrate that the
germination stimulants of S. hermonthica present in the
root exudates of maize, cowpea and
sorghum are derived from the carotenoid biosynthetic pathway. Based on these results, we
have
postulated a biogenetic scheme for the strigolactone germination
stimulants.
Miegel, D (1),
Hayton, D (1), and
Matthews, JM (1)
Seedbank
and Seedbank Management
of Orobanche ramosa in
South Australia.
1.
School of Agriculture, Food and Wine; University of Adelaide, PMB 1
Glen
Osmond, South Australia 5064, Australia.
The discovery
of Orobanche ramose
L.
in 1992 in
South
Australia has lead to an intensive research and eradication effort. Seedbank longevity studies
were
initiated in 2002 and will be discussed, twice yearly exhumations are
done but
no significant reduction has been observed.
Seed eradication with a soil drench "Bio Seed-Eradicator"
containing novel, environmentally safe active ingredients has proved
successful
with up to 98% seed death. Trial
results will be presented and discussed.
Many herbicides and adjuvants have been tested with
complete suppression
of emergence from some products.
Mainly conventional crop species have been involved but
herbicide
tolerant canola and herbicide tolerant Medicago have great potential
due to a
larger number of potent herbicides.
Management leading to eradication will be discussed.
Murdoch, AJ
(1), and Kebreab (2)
Predictive
Empirical Modeling of Parasitic Weed Life
Cycle
1. Department
of Agriculture, The
University of Reading, P.O. Box 237, Earley Gate, Reading, RG6 6AR, UK. Email:
a.j.murdoch[at]reading
.ac.uk
2. Centre for
Nutrition Modelling,
Department of Animal and Poultry Science, University of Guelph, Guelph,
Ontario
N1G 2W1, Canada.
Dormancy in Orobanche
and Striga
seeds
is
removed as a two-stage process. First, after
shedding from the mother plant, populations of dry Orobanche seeds
after-ripen (lose primary
dormancy). Increasing the temperature results in a faster
after-ripening rate
of the seed population. The second stage - conditioning - occurs at
water
potentials close to full imbibition. The rate of conditioning in the
seed
population also increases with increase of temperature. Secondary or
even
tertiary processes may interfere with dormancy loss. For example,
prolonging
the conditioning period beyond about 21 days decreases the subsequent
germination response due to a) induction of secondary dormancy and b)
at
temperatures over about 25˚C, loss of viability in the case
of Orobanche. Germination
of conditioned seeds
depends on chemical stimulation from host's roots,
temperature and water
stress. The thermal time for germination is strongly affected by water
potential. Non-linear probability models account for these processes
and
provide predictive empirical models to describe the germination
behavior of the
seed population. This paper discusses whether additive or
multiplicative models
are more appropriate for conditioning responses and explores the
implications
of these results for parasitism of crop plants.
N
Nickrent, DL
(1), and Vidal-Russell,
R (1)
The
Evolutionary Origins of
Aerial Parasitism in Santalales
1.
Department of Plant Biology, Southern Illinois University, Carbondale,
IL
62901-6509, USA.
E-mail:
nickrent[at]plant.siu.edu, romina[at]siu.edu.
Molecular
phylogenetic work in the
sandalwood order (Santalales) has progressed to the point where
multiple DNA
sequences of nuclear and plastid genes are available for nearly all of
the 146
genera. Moreover,
phylogenetic
methods have matured with the development of model-based methods such
as
maximum likelihood (ML) and Bayesian inference (BI) that more
effectively deal
with rate heterogeneity - an issue with some parasitic plant lineages. Past work showed that
aerial parasitism
evolved five times independently in Santalales, but the relative timing
of
these diversifications was not addressed. DNA sequences from five genes
were
obtained from 39 taxa representing all families in Santalales. These
data were
analyzed using ML and BI and time estimates were performed with a
Bayesian
relaxed molecular clock and penalized likelihood methods. The trees were calibrated
using
published fossil data from Santalales and an outgroup. These analyses
showed
that aerial parasitism first arose in Misodendraceae ca. 89 Mya and
subsequently in Viscaceae (81 Mya), "Eremolepidaceae" (62 Mya), tribe
Amphorogyneae in Santalaceae (53 Mya), and Loranthaceae (30 Mya). The
rapid
adaptive radiation and speciation in Loranthaceae coincides with the
appearance
of savanna biomes during the Oligocene. Reconstructing the character
"parasite
mode" on the tree suggests that all lineages except Misodendraceae
evolved from
ancestors that were polymorphic for either root or stem parasitism.
Features
found in more derived aerial parasites, such as the squamate habit,
unisexual
flowers, and loss of chlorophyll, have evolved independently and thus
represent
convergences and parallelisms.
O
Ogbebor, NO
(1), Omorusi, VI (1) and
Evueh, GA (1)
Evaluation
of Mistletoe Incidence
on Nine Rubber Clones and its Effects on Latex Yield in Nigeria
1.
Plant Protection Division/Microbiology Division, Rubber Research
Institute of
Nigeria, P.M.B. 1049, Iyanomo Benin City. E-mail: Ogbeb06[at]yahoo.com. Telephone: +08055338839
Incidence of
mistletoe on nine
rubber clones consisting of three exotic (PR107, RRIM 707 and GT1) and
six
developed clones in Rubber Research Institute of Nigeria (NIG 800, 801,
802,
803, 804 and 805) were evaluated. The effect of mistletoe on rubber
production
was also observed. The results showed that GT1 clone were more
susceptible to
mistletoe attack with disease index of 19.22. This was followed by Nig
801
clone which had a disease index of 12.23. RRIM 707 recorded the lowest
disease
index of 2.37. The experiment further demonstrated that trees with
severe
infestation gave the highest rubber production in the weights fresh cup
- lumps
and dry weights of cup - lumps.
Okazawa, A (1),
Wada, Y (1),
Fukusaki, E (1), Yoneyama, K (2), Takeuchi, Y (2),
Trehalose
Promotes Seed
Germination of a Holoparasitic Plant, Orobanche minor Sm.
and Kobayashi,
A (1)
1.
Department of Biotechnology, Graduate School of Engineering, Osaka
University,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan E-mail:
okazawa[at]bio.eng.osaka-u.ac.jp, fukusaki[at]bio.eng.osaka-u.ac.jp, kobayashi[at]bio.eng.osaka-u.ac.jp
2.
Weed Science Center, Utsunomiya University,
350 Mine-Machi Utsunomiya 321-8505, Japan E-mail:
yoneyama[at]cc.utsunomiya-u.ac.jp, takeuchi[at]cc.utsunomiya-u.ac.jp
Parasitic
plants greatly damage
crops mainly in the semiarid Mediterranean regions.
The establishment of technology to prevent their
reproduction is eagerly required.
It is well known that germination stimulants are required
for the
germination of the parasites. The
seeds have to imbibe water at suitable temperature in the dark for
several days
to have the potential to accept the germination stimulants. This process is called
conditioning. In
this paper,
metabolic profile of hydrophilic primary metabolites in seeds of Orobanche
minor
Sm. during
the conditioning period was analyzed by GC/MS.
As a result, 25 metabolites, such as organic acids, amino
acids and sugars, were identified.
Among them, the amount of trehalose significantly
increased during
conditioning. So we
investigated
the effect of exogenous trehalose on the germination.
When 0.1 to 1% of trehalose was supplied during
conditioning, the germination rates were increased 15% to 20%. This effect was also
observed with
germination inhibitors such as abscisic acid and glucose. Trehalose is hydrolyzed to
two glucose
molecules by trehalase in plants.
Validamycine A, which is an inhibitor of trehalase, was
shown to
increase the endogenous trehalose and consequently the germination
rates of O. minor, when it was
supplied during
conditioning period. From
these
results, we concluded that trehalose is synthesized during conditioning
and has
positive effect on the seed germination of O. minor.
This information might be
helpful to establishment of an
efficient system of suicidal germination to prevent parasitic weeds.
P
Pacureanu-Joita,
M (1), Raranciuc, S (1), Procopovic,
E (2), and Sava, E (1)
AO
-
548, a Sunflower Inbred Line, Carrying Two Genes for Resistance Against
a New
Highly Virulent Romanian Population of Orobanche cumana.
1. Agricultural
Research and Development Institute Fundulea, N. Titulescu, 1, 915200,
Fundulea,
Romania. E-mail: pacurean[at]ricic.ro, mariapacureanu2[at]yahoo.com
2. Agricultural
Research and Development Station, Valul lui Traian, Constanta, Romania
A
new
highly population of the parasite Orobanche cumana has attacked
sunflower crop in
Romania, in 2005 year. In the sunflower germplasm collection of
Fundulea
institute has been identified a restorer line, AO - 548, full resistant
to this
new broomrape population.
Since
this
line could be used directly as a parent to produce commercial F1 hybrid
seed,
as well as a source of resistance to broomrape in sunflower breeding
programm,
it was decided to study
the
inheritance of resistance in this line, to the new population of Orobanche
cumana.
Using the
cytoplasmic male sterile inbred line AD - 66, known to be very
susceptible to
this population of the parasite, as a female parent, progenies of a
cross with
AO - 548 (including F1, F2, and BC1 to both parents), as well as the
parental
lines, were analyzed for their reaction to this broomrape population.
The
goodness of fit of the observed vs expected segregation ratio (15:1and
3:1)
indicated that the inheritance of resistance to broomrape in the line
AO - 548
is confered by two independent dominant genes.
Palmer, AG(1),
Liang, L (1), Keyes,
J (1), and Lynn, DG (1)
ROS
production and Semagenesis in
Pathogenesis
1. Emory
University Department of
Chemistry, 1515 Dickey Dr., Atlanta, Ga. 30322
The potential
of reactive oxygen
species (ROS) such as superoxide (O2●-) and hydrogen
peroxide (H2O2)
to induce oxidative stress (damage) in biological macromolecules is
well
established. While ROS production is well-known as a byproduct of
oxidative
metabolism and co-opted by eukaryotes as a common component of the
response to
wounding and/or infection, these potent oxidants have recently been
implicated
as signaling molecules in a number of critical developmental events. In
the
parasitic plant Striga asiatica, ROS regulates
host detection and organogenesis of the
haustorium, a specialized organ for host attachment. S.
asiatica
seedlings
produce H2O2
which serves as the co-substrate with host cell wall phenols and
apoplastic
peroxidases to release haustorial inducing p-benzoquinones in a process
we have
named semagenesis. Employing a variety of H2O2-responsive
stains in conjunction with confocal, florescence, and transmission
electron
microscopys, we have localized the site of H2O2
production and characterize its regulation. These results support a
model in
which ROS generated by the parasite is a critical component of the
signaling
process and required for haustorial organogenesis. We therefore suggest
that
ROS may function in a semagenic role in the oxidation of cellular
components in
other organisms, perhaps in conjunction with other small molecules or
enzymes, generating
secondary signaling products.
Palmer, AG (1),
Liang, L (1),
O'Malley, R (1), and Lynn, DG (1)
Calcium
Mediated Transduction of
Haustorial Inducing signals in Striga asiatica
1. Emory
University Department of
Chemistry, 1515 Dickey Dr. Atlanta, Ga. 30322
The sessile
nature of plants has
dictated a life plan in which development is tightly coupled to
external
signals in order to maximize survival. Such signals are then integrated
through
internal signaling pathways (i.e. Ca2+ and/or
hormones) resulting in
developmental changes. Deciphering the mechanisms of signal integration
and
subsequent organogenesis could have substantial agricultural benefits
and may
also shed some light on the developmental plasticity common to plants
but
largely absent in many other eukaryotes. In the parasitic angiosperm Striga
asiatica,
haustorium formation is initiated by the presence of host derived p-benzoquinones
and is characterized
by a halt in vegetative growth, swelling of the root tip, and the
formation of
haustorial root hairs. As both the initiating signal and the physical
characteristics of the haustorium have been clearly defined for this
parasite, S.
asiatica
represents
an opportune system in which to explore the perception of host derived
signals,
or xenognosins, as well as pathogen development. From root hairs to
pollen
tubes directed growth, events are often mediated by elevated
cytoplasmic
calcium concentrations. Hypothesizing that both swelling and haustorial
hair
formation might be similarly regulated events we employed a variety of
calcium
chelators, channel inhibitors, and fluorescent probes to evaluate the
importance of calcium in organogenesis. Our findings suggest that the
perception of haustorial inducing xenognosin results in the rapid
influx of calcium
from an extracellular source, presumably the cell wall, which is
crucial to
further genetic and biochemical regulation. Furthermore, this work
establishes
rapid cytoplamic calcium elevation, over a 15 minute period, upon
introduction
of the signal as the earliest component in the process of haustorial
organogenesis observed to date.
Palmer, J (1)
Horizontal
Gene Transfer Gone
Wild in Parasitic and Other Flowering Plants.
1.
Department of
Biology, Indiana
University, Bloomington, IN 47405.
E-mail: jpalmer[at]indiana.edu
I will review
the published evidence
and present unpublished data showing that there has been considerable
transfer
of mitochondrial genes between parasitic plants and their host plants
during
angiosperm evolution. This transfer has occurred in both directions,
from host
to parasite and vice-versa. A model will be presented explaining why
transfers
can involve very large regions of the mitochondrial genome, why
mitochondrial
gene transfer is relatively frequent, and why chloroplast gene transfer
is
never seen.
Pérez-de-Luque,
Alejandro (1)
Mechanisms
of Resistance to Parasitic Plants: from Field Screenings to Laboratory
Microscopic Studies
1. IFAPA-CICE
(Junta de Andaluc’a), Centro "Alameda del Obispo",
çrea de Mejora y Biotecnolog’a, Apdo. 3092, 14080
C—rdoba, Spain. E-mail: bb2pelua[at]uco.es
From
about
4,000 species of parasitic angiosperms, only very few of them are weedy
and
parasitize cultivated plants. Among the main genera are Orobanche,
Striga,
and Cuscuta.
The
available control methods have not proven to be as effective,
economical and
applicable as desired. The only way to cope with the weedy root
parasites is
through an integrated approach, employing a variety of measures in a
concerted
manner. Genetic resistance remains as one of the most desirable
components in
an integrated control strategy. Because resistance is a multi-component
event,
understanding the physiological and genetic basis of such resistance at
the
different stages of the infection process will improve its utility as a
control
measure and assist in being attempts to integrate diverse mechanisms of
resistance from different sources (including wild relatives) into a
single
cultivar (i.e., pyramiding multiple mechanisms of resistance). However,
the
basic mechanisms governing resistance to parasitic plants remain
undiscovered.
Furthermore, unlike the large core knowledge base available in other
pathosystems, the molecular basis of the parasitic plant-resistant host
interactions is still at a very preliminary stage. In this way,
traditional
histological methods are valuable tools in order to preliminarily
unveil the
defensive mechanisms leading to resistance. Recently, the combination
of
histological methods with molecular techniques (molecular histology)
has been
shown to be a powerful tool to increase our understanding and knowledge
about
the infection and resistance processes. We will try to give an overview
about
what is known on the mechanisms of resistance against root parasitic
plants,
mainly centred in broomrapes (Orobanche
spp.).
Plakhine, D
(1), Tadmor, Y (1),
Levin, I (2) and Joel, DM (1)
Non-Stimulated
Spontaneous
Germination of Orobanche is
Genetically Controlled
1.
Newe-Ya'ar Research Center, ARO, PO. Box 1021, Ramat-Yishay 30095,
Israel.
E-mail:
dinap[at]agri.gov.il; tadmori[at]agri.gov.il;
dmjoel[at]volcani.agri.gov.il
2.
The Volcani Center, ARO, PO. Box
6, Bet-Dagan 50250, Israel.
E-mail:
vclevini[at]volcani.agri.gov.il
A fundamental
step in the evolution
of the angiospermous root holoparasites is their ability to germinate
only in
response to stimulants that are released by host roots.
Germination away from a host leads to
seeding death. We assumed that the trait requiring stimulant
receptivity
evolved by the development of genes that inhibit germination, and
switch off
inhibition upon chemical stimulation. By analyzing inter-specific
hybrid
populations of Orobanche cernua and Orobanche
cumana,
segregating
for spontaneous germination that occurs
without chemical stimulation, we identified genes that are involved in
germination
control. The segregation results correspond to the expectation that two
epistatic genes are responsible for this germination control. Our model
suggests that one root parasite dormancy gene (Rpdg1) is a
regulator of non-stimulated
germination, with a dominant negative control on the expression of Rpdg2 gene. We
hypothesize that Rpdg1 is involved in
seed dormancy, and Rpdg2 in the
reception or transduction of
the germination stimulus. For spontaneous germination a seed should
express the
recessive alleles of Rpdg1 and the
dominant allele of Rpdg2. Our results
agree with the 3:13
(spontaneous vs
non-spontaneous germination) ratio in the first segregating generation,
which
matches to our assumption that one parent species possess the two
dominant genes,
and the other has the two recessive genes. These results indicate that
spontaneous germination of Orobanche is genetically
controlled. Such genetic control ensures a
low incidence of this lethal trait among natural parasite populations,
and
increases the rate of its successful germination in the vicinity of
host roots.
R
Roney,
JK (1),
Khatibi, PA (1), Stromberg, VK (1), and Westwood, JH (1)
Trafficking
of Host mRNAs into
Dodder: A New Frontier in Host-Parasite Communication
1. Department
of Plant
Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA
24061-0392 USA. E-mail: westwood[at]vt.edu
Dodders
(Cuscuta spp.) have
especially open
connections to the host phloem and have been shown to obtain simple
sugars,
phloem-specific dyes, proteins, and viruses from their hosts. We have now shown that
phloem-mobile
mRNAs can also move from pumpkin (Cucurbita maxima Duch.) and
tomato (Lycopersicon
esculentum
Mill.)
hosts into
attached lespedeza
dodder (Cuscuta pentagona Engelm.).
Tomato microarrays were used to probe RNA from dodder
growing on tomato
to reveal 474 putatively mobile transcripts.
From this pool, over 50% of those tested have shown
evidence
of mobility based on sequence comparisons of reverse transcriptase PCR
products
generated from RNA of tomato, dodder grown on tomato, and dodder grown
on other
host species. To
date, 21 tomato
transcripts have been identified from dodder, including GAI, (Gibberellic
acid insensitive), which has been previously shown to be
translocated in
the phloem of tomato.
Host-to-parasite movement of mRNA indicates a potentially
new mechanism
of interspecies communication, and raises many questions. For example, are the
mobile host mRNAs
used by the parasite to gain information about host physiological
status? Does dodder
distinguish host mobile
mRNAs from its own, leading to selective accumulation or degradation of
host
mRNAs? Finally, the
ability of
dodder to form connections to taxonomically distant host plants
simplifies
identification of host mRNAs, so it is possible that dodder may be a
useful
tool for studying non-cell-autonomous RNAs in other plants.
S
Saadoun,
I
(1), Hameed, KM (2), Ababneh, Q (1), Bataineh, S (1) and Foy, CL (3)
Biological
Control of Orobanche cernua Seed
Germination Utilizing an
Indigenous Actinomycete Isolate in Jordan
1. Department
of Applied Biological
Sciences, Faculty of Science, Jordan University of Science and
Technology,
Irbid-22110, Jordan. Fax:
962-2-7201071 E-mail: isaadoun[at]just.edu.jo,
qoia_16[at]yahoo.com,
sereen_b[at]yahoo.com
2. Department
of Plant Production,
Faculty of Agriculture Jordan University of Science and Technology,
Irbid-22110, Jordan. Fax:
962-2-7201071, Emerate Prof.
VPI&SU Blacksburg, VA, USA, E-mail: hameed[at]just.edu.jo
3.
Department of Plant
Pathology, Physiology and Weed Science,
Virginia Polytechnic Institute and State University, Blacksburg, VA,
USA,
E-mail: cfoy[at]vt.edu
An indigenous Streptomyces isolate, R9,
was recognized to have
phytotoxic activity against seed germination of weeds. It was also
evaluated
for its potential activity against Orobanche cernua
seed germination under
laboratory conditions. Cell-free
culture filtrate (1 liter) of R9 (grown on glucose peptone molasses
(GPM) in
shaken broth culture for 7 days at 28˚C) was lyophilized.
Sterile distilled
water and GPM broth were used as controls. Preconditioned O.
cernua
seeds were
uniformly spread on the
surface of water agar plates and irrigated with 1 ml of either lentil Lens
esculenta
root
exudates or GR-24 (0.2 μg/l) as
germination stimulus several hours before treatment.
R9 extracts (250 µl) were transferred into wells (10 mm in
diameter) cut in the
center of each plate. Plates were incubated in a humid incubator at
25˚C for 3
days, then percent seed germination was calculated around wells using a
dissecting microscope at 45 X. Results showed 0% O. cernua seed
germination for the R9 culture
filtrates in
contrast to 31.3% to 50% and 2.3% to 8% seed
germination in the water and GMP controls,
respectively, in duplicate experiments. Hence, R9 may be considered as
a
potential source for bio-herbicides to control Orobanche.
Sandler, HA (1)
Integrating
Germination Patterns,
Chemical, and Nonchemical Options to Manage Swamp Dodder in
Massachusetts
Cranberry Production
1.
UMass Cranberry Station, 1 State Bog Road, PO Box 569, East Wareham, MA
02538,
USA. hsandler[at]umext.umass.edu
Current
recommendations in
Massachusetts cranberry production for the control of dodder, Cuscuta
gronovii,
include
the use of horticultural practices (e.g., application of uniform sand
layers)
along with the application of preemergence herbicides.
Multiple control strategies are needed
to keep dodder from significantly reducing yields on an annual basis. A 2-year project was
evaluated the
efficacy of short-term floods (24 to 48 hr) for the control of dodder. In addition, using
simulated bogs
constructed in plastic containers, the germination patterns of MA
dodder seed
has been monitored for 9 years.
Both studies should provide important information that
will help growers
improve the timing of management strategies.
Grower trials and controlled research studies with
flooding
have documented variable effects that may be related to timing the
flood to coincide
with a certain period of seedling emergence.
Dodder seeds apparently have a definitive peak of
germination in the initial year after seeding.
Peaks can still be seen in subsequent years, but they are
much
lower. Over the
course of this
9-year study, the peak germination period occurred later each year. The delay of peak
germination from
populations in the seedbank causes overlapping generations to exist in
a single
farm field. This
may contribute to
the difficulties growers have in managing dodder.
Since most herbicides targeting dodder can only be
efficacious for a specific window of time, a portion of the population
may
always escape preemergence control and provide enough viable seedlings
to cause
substantial infestations in the vine canopy.
Schneeweiss, GM
(1), Park, JM (2),
Manen, JF (3), and Colwell, AE (4)
Phylogeny
and Evolution of Orobanche and
Related Genera
(Orobanchaceae)
1.
Department of Biogeography, University of Vienna, Rennweg 14, A-1030
Vienna,
Austria. Email: gerald.schneeweiss[at]univie.ac.at
2.
Department of Systematic and Evolutionary Botany, University of Vienna,
Rennweg
14, A-1030 Vienna, Austria
3.
Conservatoire et Jardin Botaniques, Impératrice
1, CH-1292 Chambésy/Gen�ve, Switzerland
4.
U.S. Geological Survey, Western Ecological Research Center, Yosemite
Field Station,
5083 Foresta Road, El Portal, California 95318, USA
In recent
years, molecular
phylogenetic studies have greatly enhanced our understanding of the
phylogenetic relationships of Orobanche and related
genera. These data suggest splitting Orobanche into (at
least) four segregates in
agreement with previous suggestions based on morphological and
karyological
evidence. These genera show partly different evolutionary trajectories,
e.g.,
incidence of polyploidy or diversity and evolution of retrotransposons.
Irrespective of taxonomic consequences, the phylogenetic framework
allows
rigorous testing of character evolution, e.g., the evolution of genome
size or
the correlated evolution of host range and life span. Additionally, Orobanche and related
genera may show
features of general interest, such as the occurrence of horizontal gene
transfer.
Scholes
J.
(1), and Press, M. (1)
The
Molecular Basis of Susceptibility and Resistance to Striga: insights
from
Transcript Profiling
1.
Department of Animal and Plant Sciences, University of Sheffield,
Sheffield,
S10 2TN, UK
E-mail:
j.scholes[at]sheffield.ac.uk
Striga species are
among the most
devastating parasites of subsistence farming agriculture in sub Saharan
Africa
yet our knowledge of the mechanisms underlying host susceptibility and
resistance lags behind that of fungal and bacterial pathogens. Understanding these
processes at a
molecular level is a critical step in the identification of genes that
can be
used for improving crop productivity via biotechnology based
approaches, or via
the development of molecular markers for use in marker assisted
selection
programmes. In a
susceptible
interaction, the Striga
radical/haustorium attaches to the host root and the endophyte
penetrates the epidermis, cortex and endodermis finally forming xylem
continuity with the host. Once
attached, both S. hermonthica and S.
asiatica
cause profound
effects on the development and growth of the
host plant. Recently
we have
examined changes in gene expression during a susceptible interaction
between
rice and S. hermonthica using
Affymetrix oligonucleotide microarrays. Perhaps the most striking
result was the extent of the down-regulation of gene expression that
takes
place as Striga
develops on roots of the susceptible cultivar; of the 2588 genes that
were
differentially regulated, 553 were up regulated whereas over 2000 were
down
regulated. The down
regulated
genes included those purportedly involved in metabolism, cell cycle and
DNA processing,
transcription, protein synthesis and fate, cellular communication and
signal
transduction. Plants
exhibit two
different types of resistance; non host resistance where plants are
resistance
to all isolates of a particular pathogen species and host/race-specific
resistance where they are resistant to some but not all isolates of a
pathogen. In the
latter, defense
responses are triggered following the recognition by resistance gene
(R-gene)
products of specific pathogen or host derived elicitors. Whilst a large
body of
information is available concerning the molecular architecture of
resistance to
microbial pathogens very little is known about plant-plant resistance
responses. In order
to investigate
the molecular basis of resistance to S. hermonthica, changes in
gene expression were
profiled in (1) the rice cultivar Nipponbare which exhibits host
specific
resistance and (2) Arabidopsis thaliana which is a non
host to this parasite. In
both cases over 1000 genes
were significantly up or down regulated. The greatest number of genes
was most
strongly up regulated 24 hours post inoculation consistent with active
host
resistance responses. Functional
analyses revealed that large numbers of genes involved in cell wall
synthesis,
defense signaling, regulation of transcription and protein synthesis,
oxidative
stress and primary and secondary metabolism were up-regulated but there
were
differences between the host and non host interaction.
A key feature of the non host
interaction was the up-regulation of many genes (EDS1, EDS5, PAD3,
NPR1, NIMIN1,
PR2) and WRKY transcription factors involved in the salicylic acid
signaling
pathway. Finally,
susceptibility and resistance mechanisms will be considered in the
context of
physiological and metabolic interactions between host and parasite and
a brief comparison
drawn between plant-plant interactions and those involving interaction
of
plants with other taxa.
Shamoun, SF
(1), Rietman, LM (2), Askew, SE (2), and van der
Kamp, BJ (2).
Development
of a Biological
Control Strategy for Management of Hemlock Dwarf Mistletoe in Coastal
British
Columbia, Canada
1. Natural
Resources Canada, Canadian Forest Service,
Pacific Forestry Centre, 506 West Burnside Road, Victoria, BC V8Z 1M5
Canada
2. Department of Forest Sciences, Faculty of Forestry, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
The purpose of
this research is to
assess the indigenous fungi Neonectria neomacrospora (pathosystem
1) and Colletotrichum
gloeosporioides
(pathosystem 2) as biological control agents for the conifer parasite
hemlock
dwarf mistletoe (HDM; Arceuthobium tsugense). Two separate
field trials were
conducted on Vancouver Island. Treatments for pathosystem 1 involved
spraying
Stabileze formulated conidia onto unwounded and wounded HDM swellings
and cut
HDM shoots. Treatments for pathosystem 2 involved spraying Stabileze
formulated
conidia onto unwounded HDM swellings and cut HDM shoots, and spraying
Sucrose-gelatin formulated conidia onto unwounded HDM swellings. The
objectives
of both field trials were to: (1) determine the efficacy of treatments
in
establishing infection, and (2) measure the impact of infection on HDM
shoot
health and number. Results for pathosystem 1 suggest that applying
inoculum to
wounded HDM swellings had a greater impact on N. neomacrospora infection than
applying inoculum to
unwounded HDM swellings or cut HDM shoots. HDM swellings with confirmed
N.
neomacrospora
infection (isolation of the fungus and (or) presence of sporodochia)
had their
numbers of healthy mistletoe shoots significantly reduced by 1.6 or
about 36%
when compared with HDM swellings with unconfirmed infection (P=0.014). Results for pathosystem 2
showed
stabileze and sucrose-gelatin formulated conidia treatments reduced the
current
berry crop by 16-36%, respectively (P=0.05). While the results for
shoots
appeared promising, heavy background infection and/or secondary
infection,
especially on controls, limited the ability to detect clear treatment
effects.
The implications of these results in variable retention silviculture
systems and
future research will be discussed.
Stefanovic, S
(1), and Costea, M (2)
Reticulate
Evolution in the
Parasitic Genus Cuscuta
(Dodders; Convolvulaceae)
1.
Department of Biology, University of Toronto, Mississauga, Ontario L5L
1C6,
Canada
2.
Department of Biology, Wilfrid Laurier University, Waterloo, Ontario
N2L 3C5,
Canada
The frequency
and relative
importance of hybridization in plants has been an area of intense
debate. Although
this evolutionary mechanism
has received considerable attention from plant biologist, there are no
well-supported cases of reticulate evolution involving holoparasitic
plants to
date. Recent
molecular
phylogenetic analyses revealed that the subgenus Grammica, the largest
and most diverse group
of the stem parasitic genus Cuscuta, consists of
15 major clades. We
describe here five cases of strongly supported
discordance between phylogenies derived from plastid and nuclear data
and
interpret them as results of five independent hybridization events. Three of these cases
probably represent
relatively recent reticulations because each of them involves more
closely
related species, always confined within the same major clade as their
putative
parental species, and are sympatric/parapartric in distribution with
them. In contrast,
the two remaining cases
involve species whose potential progenitors are derived from different
major
groups of Grammica
and are allopatric in their present distribution.
This is consistent with more ancient hybridization
events. Exemplary
taxa
illustrating these two cases (i.e., Cuscuta subsection Denticulatae and Cuscuta sandwichiana, respectively)
are discussed in
more detail.
Sugimoto,
Y (1), Ueyama, T (1), and Yasuda, N (1)
In
vitro Production of
Strigolactones by Plant Root Cultures
1.
Graduate School of Science and Technology, Kobe University, Rokkodai,
Nada,
Kobe 657-8501, Japan
Plant tissue
culture, where aseptic
conditions are maintained and cultural parameters are easily
manipulated is a
useful technique for investigating the biosynthetic pathways of target
molecules. Preliminary screening of plant tissue cultures in our
laboratory
revealed that root cultures of Menispermum dauricum, Stephania
cepharantha
(Menispermaceae) and Lotus
japonicus
(Leguminosae) are copious producers of potent Striga
hermonthica
seed
germination stimulants. EtOAc
extracts of Menispermum and Stephania root culture
filtrates induced considerable germination of S.
hermonthica
seeds,
however, the hexane extract exhibited no activity. EtOAc and hexane
extracts of
L. japonicus root
culture filtrate contained potent S. hermonthica germination
stimulants. HPLC
analysis of EtOAc extracts of Menispermum and Stephania root culture
filtrates, each, showed one major
fraction with germination-inducing activity, while that of L.
japonicus
root culture
filtrate showed more
than seven fractions with considerable activity. (+)-Strigol was
isolated from
EtOAc extracts of M. dauricum root culture
filtrate. A major stimulant produced by Stephania
cepharantha
showed
identical chromatographic behavior and molecular mass to authentic
strigol.
(+)-5-deoxystrigol was isolated from hexane extracts of L.
japonicus
roots extract
and culture filtrate.
The strigolactones were identified on basis of NMR, UV, MS and CD
spectra and
chromatographic behaviour on HPLC. Purification and identification of S.
hermonthica
germination stimulants from EtOAc extracts of L. japonicus roots and
culture filtrate are
currently under way. Authentic (+)-5-deoxystrigol was as active as GR24
in
inducing germination of Striga hermonthica and O.
crenata
seeds.
However, it was about 10- fold more active
than GR24 in inducing O. minor seed
germination.
T
Takagi, K (1),
Okazawa, A (1), Wada,
Y (1), Trakulnaleamsai, C(1), Fukusaki, E (1), Yoneyama, K (2),
Takeuchi, Y
(2), and Kobayashi, A (1)
Photoresponse
Analysis of Phytochrome A in the Non-photosynthetic Parasitic Plant; Orobanche
minor
Sm.
1
Department of Biotechnology, Graduate school of Engineering, Osaka
University,
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. E-mail:
okazawa[at]bio.eng.osaka-u.ac.jp,
takagi_kazuteru[at]bio.eng.osaka-u.ac.jp
2
Weed Science Center, Utsunomiya University, 350 Mine-machi, Utsunomiya,
321-8505, Japan
Among
environmental factors, light
induces various morphological responses. Photoreceptors are involved in
these
responses. Among photoreceptors, phytochrome is the major red and
far-red light
photoreceptor. After light perception, phytochromes localize from the
cytoplasm
to the nucleus and control the expression of downstream genes. The
entire
network of light signaling has not yet been elucidated because of its
complexity. Therefore, we studied phyA of non-photosynthetic parasitic
plant, Orobanche
minor.
This plant
cannot photosynthesize and acquires its energy from the host plant. It
is
thought that Orobanche minor has the light
signaling system related to photosynthesis
partially altered, but it retained the function necessary to regulate
morphogenesis. The amino acid sequence of OmphyA was
compared to that of AtphyA from Arabidopsis
thaliana.
The result
revealed that OmphyA has 26
amino acid substitutions
and 71% sequence identity. These substitutions are largely located
around
functional domains. Therefore, we compared the physiological responses
of O.
minor
with
photosynthetic plants to find functional differences. As a result, OmphyA has the
same biological
characteristics as its counterparets in green plants. For the
photoresponses, OmphyA has the
same role as the green
plant in germination and accumulation of anthocyanin. OmphyA plays an
opposite role in
inhibition of the stem elongation. By the usage of A. thaliana, it was
revealed that the
expression level of genes involved in phyA signal network was different
in OmphyA
and AtphyA
transfected protoplasts. These
results suggest that OmphyA function
is different from that of AtphyA, and these
differences may
attribute to amino acid substitutions of OmphyA.
Tennakoon, KU
(1), Bolin, JF (2),
and Musselman, LJ (2)
Structural
and Functional
Attributes of the Hypogeous Root Holoparasite Hydnora triceps Drege
& Meyer (Hydnoraceae)
1.
Department of Botany, University of Peradeniya, Peradeniya 20400, Sri
Lanka.
E-mail: kushant[at]pdn.ac.lk
2.
Department of Biology, Old Dominion University, Norfolk, VA 23529, USA. E-mail: jbolin[at]odu.edu,
lmusselm[at]odu.edu
Acholorophyllous
root holoparasites
with extremely reduced vegetative bodies, Hydnora spp. are the
only known angiosperms
lacking leaves and scales. Hydnora occur in the
arid regions of Africa and the southern
portion of the Arabian peninsula. Five species are currently recognized
in this
genus. The most remarkable species, H. triceps completes its
entire lifecycle
below ground. The reduced vegetative structure of H. triceps raises two
important questions: (i)
How does the vegetative body grow and attain its distinctive structural
entity?
and (ii) By what means does it make intimate connections with its host
and
fulfill water and nutrient requirements? The vegetative body consists
of "pilot
roots", poorly studied structures bearing haustoria and flowers. Our
studies showed
a "chimeral" apical structure and a protective layer of cells similar
to a root
cap at the growing tip. However, eustelic, endarch and collateral
vascular
bundles and the continuous pith indicate that pilot roots are stems.
Increased
girth is due to the fascicular cambium, periderm and strands of cells
distributed in the main vegetative body similar to a primary thickening
meristem. The haustorium and the reproductive structures of H.
triceps
initiate
exogenously from the "root
bumps" (outgrowths of the vegetative body). An endophytic primodium
penetrated
the host root with a stratified meristem giving rise to xylary and
pholic
hyphae, and transfer cells.
Tennakoon, KU
(1)
Potential
of Establishing Root
Hemiparasitic Sandalwood (Santalum album
L.) as a NTF Species in
the Buffer Zones of Forests and
Degraded Lands in Australasia: a Sri Lankan Experience
1.
Department of Botany, University of Peradeniya, Peradeniya 20400, Sri
Lanka.
E-mail: kushant[at]pdn.ac.lk
Santalum
album
has received
much attention during
the recent years in Australasia due to its potential as a valuable NTF
species.
Sandalwood oil is used to prepare expensive perfumes, cosmetics and a
range of
medicines. One kg of Sandalwood oil is currently traded around US$
3,000. The
potential exists to reduce harvesting pressure on natural stands of S.
album
by
establishing plantations. Around
80% germination was obtained when seeds were treated with 750 ppm
gibberellic
acid. When the seedlings were grown in equal parts of sand, soil and
farm yard
manure, a significantly greater (p<0.001) height, root collar
diameter and
leaf number were obtained. A significantly higher (p<0.01)
performance of
sandalwood seedlings, with respect to light, was observed between 25% -
50%
(1300 _ 915 _ mol m-2 s-1) shade and with respect to the pot hosts,
with Mimosa
pudica
and Tithonia
diversifolia.
The
best growth in terms of plant height, root collar diameter, root
biomass, over
a 3 year field establishment trial was obtained in the treatment where
a
sandalwood plant was surrounded by four Sesbania grandiflora plants at a
spacing of 1.5 m apart
from each other. Field studies showed the potential of a range of
native host
plants that could be intercropped with Sandalwood. This improves the
enhancement of natural biodiversity, creation of new habitats and
conservation
of plant species in degraded areas. All this would not have occurred
with out a
commercial incentive to growers, which in this case is Sandalwood.
Thorogood, CJ
(1), Rumsey, FJ (2),
and Hiscock, SJ (1)
Speciation
and Host Specificity
in Orobanche
1. School of
Biological Sciences,
University of Bristol, Woodland Road, Bristol, BS8 1UG, U.K.
E-mails:
chris.thorogood[at]bristol.ac.uk, Simon.Hiscock[at]bristol.ac.uk
2. Natural
History Museum, Cromwell
Road, London SW7 5BD, UK. E:
mail: .rumsey[at]nhm.ac.uk
Orobanche (broomrapes)
are obligate parasites
which attach to the roots of other plants as seedlings. Each species
has a
preferred host-range and while some species parasitize variety of
plants,
others are much more host-specific. It is possible that speciation in
parasitic
plants, like Orobanche, might be
triggered by a shift in host preference. Continued divergence
between parasite populations could then be driven by ecological
isolation
and/or selfing. We speculate that changes in host preference could be
triggered
by hybridization if hybrids possessed transgressive phenotypes that
pre-adapted
them to parasitism of a new host. We are investigating this hypothesis
by
studying an Orobanche complex in the
UK in which two species, O. minor and O.
picridis
merge, and
intermediate
morphotypes, possibly hybrids between them, occur. The parent
species'
distributions are restricted to where their preferred hosts occur,
while
putative hybrids appear to occupy a new niche on coastal turf.
Preliminary
Inter-simple sequence repeat marker data shows evidence of
introgression,
suggesting that intermediate morphotypes are hybrids. We are also using
rhizotrons (a bioassay in which host and parasite are cultivated) to
investigate
the host preferences of O. minor, O.
picridis
and the
putative hybrids to determine whether hybridization
can cause a change in host preference. Ultimately our goal is to
determine
whether hybridization and shifts in host specificity contribute to
speciation
in parasitic plants.
Timko,
MP
(1),Gowda, BS (1), Li, J (1), and Lis, K (1),
Deciphering
the Interaction of
Striga with Hosts and Non-hosts
1.
Department of Biology, University of Virginia, Charlottesville, VA
22904 USA
E-mail: mpt9g[at]virginia.edu
The
parasitic weeds Striga gesneroides (witchweed)
and Alectra vogelii are among the
major constraints to
the production of cowpea, Vigna unguiculata (L.) Walp., one
of the most
important food and forage legumes in the semi-arid tropics of West and
Central
Africa. There is considerable variation in host specificity among
isolates of S.
gesnerioides. Based on host differential
response and
genetic diversity analysis at least seven races of S.
gesnerioides
have been
identified within the
cowpea-growing regions of West Africa that specifically parasitize
cowpea.
Similar evidence also exists for multiple races of A. vogelii parasitic on
cowpea. Race
specific resistance genes have
been identified and mapped into two linkage groups (LG1 and LG6) within
the cowpea
genetic map. How race specific resistance is mediated at the cellular
and
molecular level remains to be determined. Studies are underway aimed at
identifying the factors that determine host specificity and virulence
in
parasitic angiosperms and to address whether specific avirulence genes
exist in
S. gesnerioides that
correspond to the race-specific resistance genes identified in cowpea
and if
these form the basis for a gene-for gene interaction as recognized in
other
plant-plant pathogen interactions. Our findings indicated that
developmental
processes occurring post-germination and attachment are likely more
important
in limiting successful host parasite interaction. Progress in this work
will be
discussed.
Tomilov,
A
(1), Tomilova, N (1), Filappova, T (1), Gunathilake, P (1), Wu, D-Y
(1), Hoang,
N (1), and Yoder, JI (1)
Early
Haustorium Development in Triphysaria: A
View from Inside the Nucleus.
1. Department
of Plant Sciences,
Mail Drop 3, University of California-Davis, Davis, California
95616-8780,
USA
style="color: windowtext;">jiyoder[at]ucdavis.edu
The
competence to develop invasive haustoria is the defining feature of all
parasitic species. We are identifying genes in the root parasite Triphysaria that are
responsible for haustorium
development in order to understand the evolutionary origin of this
pathway in
Orobanchaceae. In the longer term we are interested in learning the
degree to
which similar genetic pathways have been recruited in other parasitic
families.
Working under the assumption that genes associated with haustorium
development
will be differentially regulated soon after contact with a host root,
we made
cDNA libraries representing transcripts expressed in Triphysaria root tips
after treatment with
natural and chemical haustorial inducers.
Nucleic acid hybridizations were performed to enrich the
libraries for
transcripts either up or down regulated after treatment with host
roots, host
root exudates, or purified haustorial inducing chemicals. These
enriched libraries,
as well as a library of cDNAs enriched for full length transcripts,
were
sequenced by the DOE Joint Genome Institute. Sequences of the ESTs and
assembled unigenes are available as Fasta files at
http://www.plantsciences.ucdavis.edu/yoder/lab/Sequence_index.html.
Based on
the distribution of transcripts in different libraries and on
annotations of
their putative functions, we selected a subset of genes for analysis by
cDNA
arrays. Candidate genes isolated on the basis of their expression
profiles are
being subcloned into RNAi vectors and introduced in Triphysaria roots by
infection with Agrobacterium
rhizogenes
to
monitor their functions in planta. Results and
status of this work will be discussed.
V
van
der
Kooij,TAW (1,2), Krupinska K (1), and Krause, K(1,3)
Characterization
of the
Tocochromanol Content and Composition of Different Species of the
Parasitic
Flowering Plant Genus Cuscuta
1.
Institute of Botany, Plant Cell Biology,
Christian-Albrechts-University, 24098
Kiel, Germany E-mail: kkrupinska[at]bot.uni.kiel.de
2.
Present address: HZPC research, P.O. Box 2, 9123 ZR Metslawier,
Netherlands.
3.
Present address: Institute for Biology, University of Troms, 9037
Troms,
Norway. E-mail: kirsten.krause[at]ib.uit.no
The
holoparasitic plant genus Cuscuta comprises
plant species with different degrees of plastid
functionality, ranging from intact photosynthetically active
chloroplasts, via
plastids with impaired protein production and gene expression to
plastids with
reduced plastome gene content. While some species are
photosynthetically active
and have a chlorophyll and carotenoid composition similar to
non-parasitic
plants, other species are non-photosynthetic and do not contain any
chlorophyll. To investigate whether the tocochromanol content and
composition
is related to the photosyn_thetic capacity of the species, the overall
content
of tocochromanols and the levels of the individual tocochromanols were
determined in stem sections of eight Cuscuta species. All
species including the
non-photosynthetic ones contain plastoquinone and tocochromanols at
variable
levels. In addition, unusual tocochromanol species were detected in C.
japonica
and C.
grandiflora.
No
correlation between tocopherol content and carotenoid content or
chlorophyll
content was observed indicating a function of the tocopherols unrelated
to
antioxidative tasks.
Virupakshaiah,
DBM (1), Ameresh, SH
(1), and Mirji, SB (1)
Structure
Analysis of Computer
Generated Homologous Models of pm3 Protein in Triticum
aestivum
(Wheat)
1.
Depart of Biotechnology, Basaveshwar Enineering College, S.Nijalingappa
Vidhyanagar, Bagalkot-587 102, Karanataka, India, Post Box No: 53,
Phone:
08354-234060, Fax: 08354-234204, E-mail: veerudbm1[at]rediffmail.com
Most of the
plant protein structures
have not been structurally characterized.(either by NMR or X-ray
crystallography). In our research we made an effort to generate
computer built
model for powdery mildew resistant protein(f allele) found in Triticum
aestivum
(bread
wheat) cultivar, michigan amber and also find homologous models to this
protein. This protein is also called as pm3f protein and belongs to a
group of
pathogenesis related (pr) proteins. Structural analysis of this protein
and its
homologous models can help in studying their interaction with the
target macro
molecules in the attacking fungi with advent of artificial gene
synthesis
technique, the information retrieved from such a structural analysis
can help
in cloning and gene transfer experiments in those wheat cultivars which
lack
the resistance to powdery mildew.
W
Wegmann K (1)
2000
Years of Observation,
Knowledge and Research on Orobanche
1.
Center of Molecular Biology of Plants, University of Tuebingen, Auf der
Morgenstelle 5, D-72076 Tuebingen, Germany E-mail: Wegmann[at]uvvg.ro
A historical
survey will be
presented on Orobanche, beginning
with the first observations and descriptions, followed by
the period of collecting and classification of Orobanche species in
Linn's taxonomic system.
Orobanche
species have been collected in herbaria or they were preserved in
alcohol
(Racovita in Romania). Orobanche species up to
date would have remained botanical
curiosities among the wildflowers, if not some of them turned
aggressive and
became agricultural pests. The aim of Orobanche control became
the driving force
for intensive agricultural research. Agricultural problems also led to
the
organization of special Orobanche workshops
besides the International Parasitic Weeds
Symposia. When plant physiologists and plant biochemists became
interested in Orobanche /host systems
and Orobanche development
increasing complexity
became evident. Important steps in revealing the sophisticated systems
will be
emphasized, some problems in understanding Orobanche life will be
pointed out. Moreover,
the question will be asked, why most Orobanche species die
back and need to be
protected, why they have not become agricultural pests. What is the
future of Orobanche research?
Williams, AM
(1), and Virtue, JG (1)
Calculation
of Growing Degree
Days to Determine Optimum Timing of Herbicide Application for Control
of
Branched Broomrape Orobanche ramosa in
Pastures.
1.
Department of Water Land and Biodiversity Conservation, South
Australian
Government, GPO Box 2834, Adelaide, South Australia 5001. E-mail:
williams.anna[at]saugov.sa.gov.au virtue.john[at]saugov.sa.gov.au
In South
Australia (SA), branched
broomrape Orobanche ramosa is the subject
of a national eradication program.
Inspections, quarantine protocols and control treatments are in place
for
affected properties in the Murray Mallee region of SA to limit any
further
spread of branched broomrape and eliminate soil seedbanks in mapped
infestations. At present the weakest link in the eradication program is
the
difficulty of controlling branched broomrape in pasture paddocks. The
pastures
in the area are generally unimproved and contain a range of host
species of
branched broomrape. Management of branched broomrape in pastures is
difficult
but can be achieved by spraying sulfonylurea or glyphosate herbicides
onto weed
hosts prior to broomrape emergence. The timing of herbicide sprays is
important
to target smaller attachments.
Assessment of
the timing of
broomrape attachments and development until emergence was conducted in
the
field during the 2006 season. Additionally, observations were also
collected on
hosts grown in a glasshouse. The broomrape development data was
correlated to
growing degree days (GDD) using soil temperature and a base temperature
of 0oC.
Broomrape attachments began around 500 GDD after the start of the
growing season,
or after planting the hosts in the glasshouse. Emergence occurred 1000
GDD
after attachment both in the glasshouse and in field conditions. Based
on 2006
results, optimum herbicide application time would have been from 250
GDD after
attachment to approximately 750 GDD after attachment. Further field and
glasshouse observations are being conducted during 2007 to determine if
the GDD
model can accurately predict broomrape emergence in a different season
and on
different hosts.
X
Xie, X (1),
Awad, AA (1), Yoneyama,
K (1), Sekimoto, H (2), Kusumoto, D (1), Takeuchi, Y (1), Yoneyama, K
(1)
Qualitative
and Quantitative
Differences of Strigolactone Exudation Determine Host Specificity of
Root
Parasites Orobanche and Striga
1.
Weed Science Center, Utsunomiya University, 350 Mine-machi, Utsunomiya,
321-8505, Japan. E-mail:
xmoonlighter[at]hotmail.com,
aymanalawad[at]hotmail.com, fragrance0917[at]yahoo.co.jp,
kusumoto[at]cc.utsunomiya-u.ac.jp, takeuchi[at]cc.utsunomiya-u.ac.jp,
yoneyama[at]cc.utsunomiya-u.ac.jp.
2.
Department of Plant Science, Faculty of Agriculture, Utsunomiya
University, 350
Mine-machi, Utsunomiya, 321-8505, Japan. E-mail:
hitoshis[at]cc.utsunomiya-u.ac.jp.
Strigolactones,
originally
identified as germination stimulants for root parasitic weeds, Striga,
Alectra,
and Orobanche, are now
recognized as important
chemical signals for arbuscular mycorrhizal (AM) fungi symbionts. Even non-mycotrophic
plants like
spinach exudes strigolactones, indicating that strigolactones may have
some other
important functions in plants and/or in rhizosphere communities. In addition, plants appear
to exude
mixtures of strigolactones along with other unknown germination
stimulants,
probably including non-strigolactones.
It is likely that the amounts and composition of these
stimulant
mixtures may vary with plant species, their growth stages, and their
growth
conditions including nutrient availability.
Furthermore, for example in sorghum, different cultivars
exude different mixtures of strigolactones.
These results suggest that quantitative and qualitative
differences of strigolactones have some effects on host recognition by
AM fungi
and root parasitic weeds. Examples
of qualitative and quantitative differences of strigolactones among
host and
non-host plants will be presented and discussed in relation to
host-recognition
by AM fungi and root parasites.
Y
Yonli,
D (1), Traoré, H (1),
Sérémé, P (1), Hess, DE (2),
and Sankara, P (3)
Integrated
Striga
hermonthica
Management Based Fusarium
1.
Institut de l'Environnement et de Recherches Agricoles, 04
BP 8645, Ouagadougou
04, Burkina Faso. E-mail:
yonlidjibril[at]yahoo.fr or djbril_yonli[at]univ-ouaga.bf
2.
Merry Lea Environmental Center of Goshen College, P.O. Box 263, Wolf
Lake, IN
46796, USA.
3.
Université de Ouagadougou, Unité de formation et
de recherche en sciences de la
vie et de la terre B.P. 7021, Ouagadougou, Burkina Faso.
Cereal
production is mortgaged by Striga hermonthica (Del.) Benth.,
the main angiosperm
root parasitic. The pathogenicity of endogenous Fusarium isolates
against S. hermonthica was evaluated
in the laboratory and
an application method was investigated under greenhouse conditions.
Cultural
control methods against the parasitic plant were also evaluated under
field
conditions in order to combine them with biological control using Fusarium in Sorghum field. The
results of our study
showed that the spores and lyophilized culture filtrate of some Fusarium isolates
significantly reduce
germination of S. hermonthica seeds.
Furthermore, applying spores from
Fusarium
isolates to
the seeds of S.
hermonthica
led to a
potential reduction of the germination rate of Striga of more than
78% with eight Fusarium isolates. The
effectiveness of the
lyophilized culture filtrate to inhibit germination of S.
hermonthica
is related to
the amount and type of
isolate used in the experiment. Thus, the complete inhibition of
germination is
observed starting from 33 mg/ml with the lyophilisate of four Fusarium isolates and at
67 mg/ml with that
of three others. This study showed the capacity of Fusarium spores to kill S.
hermonthica.
Application
of spores of two
Fusarium
isolates on
the
plants of the parasite led to a reduction of more than 77% of S.
hermonthica
dry biomass.
Two substrates were
used to produce the inoculum-based Fusarium: compost and Sorghum chopped straws.
Incorporating the
inoculum into the soil to control S. hermonthica was effective.
By using this method,
six Fusarium isolates showed
potential effectiveness in controlling S. hermonthica. However,
their effectiveness
depends on the growth medium. Burial of S. hermonthica seeds up to 10
cm from the sowing
hill containing the inoculum did not influence the performance of Fusarium isolates to
control S.
hermonthica.
On the
other hand, burial depths of 10 cm below the sowing hill containing the
inoculum influenced the effectiveness of Fusarium isolates.
Irrespective of the
substrate, the increase of the burial depth led to a reduction of the
number of
Fusarium isolates
effective against Striga. The
evaluation of the pathogenicity of Fusarium isolates in
field revealed the
possibility to integrate biological control to cultural control methods
in the
management of S. hermonthica. The
incorporation of inoculum-based compost into the soil
led to a great reduction of number of emerged S. hermonthica in plots.
Integrated management of S.
hermonthica
combining use of Fusarium, a tolerant Sorghum variety, trap
crops or
organic/mineral fertilizer reduced more significantly infestation of S.
hermonthica
in the field
and subsequently enhanced crop yield. Results from these
experiments of different control methods against S.
hermonthica
enabled us to
propose an integrated
management approach of the parasitic plant. However, there is need for
improved
bioherbicide formulations and delivery systems to enhance the potential
role of
biocontrol in integrated management of the parasite in Burkina Faso.
Yoneyama, K
(1), Sekimoto, H (2),
Takeuchi, Y (1), and Yoneyama, K (1)
Nitrogen
and Phosphorus
Deficiencies Promote the Production and Exudation of 5-Deoxystrigol in
Sorghum
1. Weed Science
Center, Utsunomiya
University, 350 Mine-machi, Utsunomiya 321-8505, Japan E-mail:
fragrance0917[at]yahoo.co.jp, takeuchi[at]utsunomiya-u.ac.jp,
yoneyama[at]utsunomiya-u.ac.jp
2. Faculty of
Agriculture,
Utsunomiya University, 350 Mine-machi, Utsunomiya 321-8505, Japan. E-mail:
hitoshis[at]utsunomiya-u.ac.jp,
Strigolactones
secreted from plant
roots are important host recognition signals for root parasitic weeds
and
symbiotic arbuscular mycorrhizal (AM) fungi.
In red clover, a host of Orobanche, a reduced
supply of phosphorus,
but not of nitrogen or other mineral nutrients, significantly promoted
the
exudation of orobanchol. By
contrast, deficiency of nitrogen as well as phosphorus markedly
promoted the
exudation of 5-deoxystrigol from sorghum, a host of Striga.
When sorghum plants were
subject to deficiency of both
nitrogen and phosphorus, the exudation of 5-deoxystrigol increased only
slightly as compared to those under phosphorus deficiency. Sorghum plants
continuously exuded 5-deoxystrigol
under nitrogen deficiency, but the exudation was suppressed within 24 h
after
adding nitrogen to the growth media.
Similar results were obtained with phosphorus treatments. Nitrogen and phosphorus
deficiencies
also increased 5-deoxystrigol contents in sorghum roots. In both cases the increase
was
comparable to that in the root exudates.
These results suggest that strigolactones may be released
rapidly after
their production in the roots.
Unlike the situation in the roots, nitrogen and phosphorus
deficiencies
did not increase the trace amounts of 5-deoxystrigol that are found in
sorghum
shoots.
Yoshida, S (1),
and Shirasu, K (1)
Agrobacterium-Mediated
Transformation of Striga hermonthica
1.
Plant Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi, Yokohama,
230-0045
Japan, E-mail: satokoy[at]psc.riken.jp, ken.shirasu[at]psc.riken.jp
Striga spp. (witchweeds) are major agricultural pests which infest important crops in sub-Saharan Africa and parts of Asia. To develop control methods against Striga infestation, understanding the molecular basis underlying its parasitism is of particular importance. However, molecular knowledge about Striga infection is still limited. Reverse genetic approaches are powerful tools to assess unknown gene function and identify functional genes. Establishment of a transformation system is a critical step to conduct reverse genetic experiments. In the present study, we aim to establish transformation methods of Striga hermonthica using Agrobacterium. Striga is an obligate root parasite which is unable to live without its host in natural conditions. Therefore we initially developed axenic culture conditions of S. hermonthica. Surface sterilized S. hermonthica seeds were germinated and grown under axenic conditions. Striga plants were able to develop plant architecture with shoots and root-like structures in the presence of sufficient nutrients and carbon source in the media. Callus formation and emergence of shoot and root-like structures were controlled by a balance of auxin and cytokinin. We tested transformation of aseptically grown S. hermonthica via Agrobacterium tumefaciens or A. rhizogenes using green fluorescence protein (GFP) as a marker. Our preliminary results showed that A. rhizogenes-mediated transformation successfully generated GFP expressing hairy roots of S. hermonthica.