12.4.1. horizontal gene transfer in the evolution of plant
mitochondrial genomes
J. D. Palmer;
Indiana University, Bloomington, IN, United States.
I will first give a brief overview of the remarkable propensity
of plant mitochondrial genomes to take up foreign DNA, from the
chloroplast and nucleus via intracellular gene transfer and from
other plant mitochondrial genomes via horizontal gene transfer.
I will then focus on the latter topic, presenting recent work
from my lab on the extent, frequency, functional consequences,
and mechanisms of plant-to-plant horizontal transfer of mitochondrial
genes. Special emphasis will be placed on the role of parasitism
in horizontal transfer and on the basal angiosperm Amborella
trichopoda, whose mitochondrial genome is exceptionally full
of foreign genes, acquired from a wide range of angiosperm and
moss donors. The implications - both negative and positive - of
widespread horizontal gene transfer for the utility of plant mitochondrial
genes as phylogenetic and chronological markers will be discussed.
12.4.3. Evolution of RNA editing sites and its impact on
phylogenetic signal in plant mitochondrial genes
C. dePamphilis;
Pennsylvania State University, University Park, PA, United States.
We present an analysis of sequence evolution and phylogenetic
signal in three mitochondrial genes -cox1, matR, and atp1 - that
we have sampled from diverse flowering plant species. Phylogenetic
signals are present in these genes that are mostly congruent with
chloroplast and nuclear gene phylogenies, and contribute to the
resolution of challenging problems in angiosperm phylogeny including
origins of parasitic angiosperms and the phylogenetic position
of key basal lineages. Several noteworthy phenomena were observed,
including horizontal capture of host plant DNA by parasitic plants
and evidence of a chimeric atp1 gene containing a portion of a
local host plant atp1 gene. Abrupt reversals of the editing status
(Riveting) of all editing sites has occurred repeatedly, implying
frequent retroprocessing and recombination events involving edited
mitotranscripts. These processes could drive high rates of correlated
sequence evolution at editing sites, creating processed paralogs
and destabilizing traditional concepts of homology. The impact
of RNA editing on phylogenetic analysis is examined to revisit
predictions made in an earlier study.
12.9.3. Hydnoraceae and its systematic affinities with Piperales
D. L. Nickrent1, A. Blarer2;
1Southern Illinois University, Carbonale, IL, United States, 2Institute
of Systematic Botany, Zurich, Switzerland.
In a previous investigation, the holoparasitic Hydnoraceae clade
(Hydnora, Prosopanche) was placed within Piperales;
however, its exact affinity remained unresolved. More recently,
a data set of 6 genes (nuclear, chloroplast, mitochondrial) for
three outgroup and 16 Piperales taxa was constructed. Branch and
bound analysis gave one tree with relationships fully resolved
for Piperaceae (5 genera) and Saururaceae (4 genera). In contrast,
the Aristolochiaceae (4 genera), Lactoridaceae (Lactoris)
and Hydnoraceae clades remained unresolved, even when faster-rate
parasites were removed. Aristolochiaceae is composed of two strongly
supported clades: Asarum plus Saruma (Asaroideae)
and Aristolochia plus Thottea (Aristolochioideae).
A sister relationship between Hydnoraceae and the latter received
moderate bootstrap support. Morphological divergence and branch
lengths on molecular trees indicate a comparatively high degree
of evolutionary change in this group, thus we recognize four clades
(families): Aristolochiaceae s. str., Hydnoraceae, Lactoridaceae,
and Asaraceae.
P0479. Acquisition of root hemiparasitism and other life
history traits in Santalales
V. Malécot1, D. L. Nickrent2;
1UMR A 462 - Institut National d'Horticulture, Angers, France,
2Southern Illinois University, Carbondale, IL, United States.
Based on molecular analyses, we examined the acquisition of hemiparasitism
in Santalales, particularly Olacaceae s.l. Mapping of life history
characters on molecular cladograms suggests a single origin for
an ancestral root hemiparasite that can be assumed to be one of
two ecological types. The first is an undershrub with relatively
small fruits. This type, likely occurring in a humid forest, is
reminiscent of the extant genus Ptychopetalum. The second
type is a small tree with relatively large fruits. This type likely
occurred in dryer areas (e.g. margins of humid forests and savannas)
and is reminiscent of the genus Ximenia. After the acquisition
of root hemiparasitism in Olacaceae, additional trends include:
the acquisition of accrescent structures around fruits, large
tree habit (Ongokea), and hummingbird pollination (Chaunochiton).
Other trends seen in Santalales include: five independent acquisitions
of the mistletoe habit; several independent derivations of an
herbaceous habit within Santalaceae; reduction in leaf size, venation
and changes in phyllotaxy (Santalaceae and Loranthaceae); and
pollination syndromes (Loranthaceae).
7.12.3. Gender in the mistletoe Loranthus europaeus
females work harder
G. Glatzel1, M. Popp2;
1Institute of Forest Ecology, Vienna, Austria, 2Department für
Chemische Ökologie und Ökosystemforschung, University
of Vienna, Vienna, Austria.
The mistletoe Loranthus europaeus is trioecious with small
flowers, which is a rare exception among the Loranthaceae, which
usually have brightly coloured, bird pollinated hermaphroditic
flowers on the same plant. In L. europaeus the population
of hermaphroditic plants is functionally male, as almost all flowers
are shed once the pollen is spent and very view fruits develop.
Male and female plants differ in their morphology and physiology.
Male plants are more ortho geotrophic and stout and less pendulous
than female plants. Water potential is lower in female plants
when compared to male plants under the same conditions. Autumnal
leaf abscission is significantly later in females. This indicates
that female plants have to work harder to support fruit development
and maturation. Foliar element analysis as well as stable isotope
analysis is currently performed and the results will be presented
at the congress.
P0269. Branches anatomy of Fraxinus uhdei (Wenzing)
Lingelsheim and Prunus persica Batsch. infected by Cladocolea
spp. (Mistletoe)
C. De la Paz Pérez Olvera, J. Ceja Romero;
Universidad Autónoma Metropolitana Iztapalapa, Div. C.
B. S., Depto. de Biología, México, D. F., Mexico.
True mistletoes are parasitic flowering plants. Seeds are disseminated
by birds and deposited on host plants reducing their growth. Samples
of 5 branches of Fraxinus uhdei and Prunus persica were
collected in Mexico City. Blocks of 1 cm3 were obtained. Slides
with typical cuts of the infected zone and the healthy zone were
made. The wood of the two species has ring porous, their vessels
are solitary and radial multiples, vessels pits are alternate.
Its perforation plates are simples, rays have 1 to 4 cells and
are heterogeneous and present fibre tracheids. The vessels in
P. persica have helical thickenings and the outline is
angular and the axial parenchyma is scanty diffuse. In F. uhdei
the vessel outline is rounded and the axial parenchyma is
of many types. The wood of mistletoe present diffuse porous. Vessels
are solitary and clusters with the outline rounded, with pits
alternate and simple perforation plates, present vascular tracheid.
The axial parenchyma is in bands, present fibre tracheids. Rays
are heterogeneous with 1 to 4 series. Both parenchyma types have
abundant starch. The host anatomy is modifing when mistletoe penetrates,
forming abundant contents.
P0275. Germination of a Tropical Mistletoe, Cladocolea
loniceroides (Van Tieghem) Kuijt Loranthaceae
R. V. Cid1, J. G. Márquez1, M. Ponce1, M. E. Engleman2;
1Facultad de Ciencias, México, d.f., Mexico, 2Colegio de
Posgraduados, Montecillo, Edo. México, Mexico.
This mistletoe grows as a hemiparasite on various trees that may
have economic value for fruit, lumber or as ornamentals. The tree´s
physiology may be affected so severely that it eventually dies.
Many aspects of floral biology, germination and establishment
have not been described for this plant. In this paper, we describe
germination, penetration of the host, and establishment. Samples
of mature fruits germinating and developing on the host were obtained.
Standard Microtechnique, light and Scanning Electron Microscopy
(SEM) are used. We describe results with microphotography. The
fruit adheres to the host with viscin and mucilage, which originate
in the middle layer of the fruit wall. A holdfast is formed during
the germination. By means of haustorium and a penetration organ,
the haustorium penetrates and becomes anchored in the xylem. A
knowledge of these mechanisms of establishment may help devise
methods of control of this mistletoe.
P1542. Haustorium type, endophytic system form and vegetative
reproduction in four Scurrula L. species
from Nepal
M. P. Devkota1, G. Glatzel2, C. Calvin3;
1Botany Department, Amrit Campus, Thamel, Kathmandu, Nepal, 2Institute
of Forest Ecology, BOKU, Vienna, Austria, 3Department of Biology,
Portland State University, Portland, OR, United States.
Epicortical roots (ER) occurred in all Scurrula species
regardless of host or elevation. Primary and secondary haustoria
evoked a wood-rose response by host. Wood-rose form varied between
and within species. Primary haustorium structural differences
allowed classification into (1) flanging endophyte, (2) flanging
endophyte with radial shafts, and, (3) sinker endophyte. Scurrula
elata and S. gracilifolia differed in haustorial form
on different hosts, and S. elata had the widest host range
due to its specific haustorial and endophytic system plasticity.
Epicortical roots of Scurrula resembled those of other
Old World species in origin, morphology and branching pattern,
but differed from those of New World species. The formation of
secondary haustoria and root-borne shoots by ERs was common, but
their frequency varied depending on the age of the mistletoe and
the length and vigour of epicortical roots.
P0775. Biogeography and phylogeny of the sandalwood genus
Santalum (Santalaceae) based on sequence data and morphology
D. T. Harbaugh, B. G. Baldwin;
University of California, Berkeley, CA, United States.
Phylogenetic analyses using a combination of morphological and
sequence data (ITS, ETS, 3'trnK intron and trnG
intron) from all currently recognized taxa in Santalum provide
evidence for broadscale, historical biogeographic patterns in
the genus. A wellsupported basal grade of taxa from Australia
supports an origin of the genus on that continent. Multiple long-distance
dispersal events must be postulated to account for the distribution
of Santalum in India and the Pacific. As previously proposed,
the Hawaiian species recently treated in sect. Hawaiiensia
(S. ellipticum and S. paniculatum) are evidently
more closely related to one another than to the other Hawaiian
endemics, S. freycinetianum and S. haleakalae, recently
treated in sect. Santalum and appear to have resulted from
two independent colonization events to Hawaii. The lineage including
S. freycinetianum and S. haleakalae also includes
S. boninense from the Bonin Islands and S. insulare
from French Polynesia, Cooks Islands, Henderson Island and
the Marquesas Islands, which indicates that Hawaii may act as
a source for dispersal to island groups in the South Pacific and
the Western Pacific.
P2044. Novel ribosome inactivating proteins (RIPs) from
Himalayan Viscum album (L.)- potential biomolecules for
bioprospecting
V. Mishra 1,2, R. S. Sharma3, S. Bilgrami2, M. Paramasivam2,
S. Yadav 2, C. R. Babu1,3, T. P. Singh2;
1Department of Botany, University of Delhi, Delhi-110 007, India,
2Department of Biophysics, All India Institute of Medical Sciences,
New Delhi-110 029, India, 3Centre for Environmental Management
of Degraded Ecosystems, University of Delhi, Delhi-110 007, India.
Ribosome inactivating proteins (RIPs) of Viscum album constitute
the active principle of traditional tumor therapy in Europe. Himalayan
V. album populations showed high morphological diversity.
To assess the prospecting potential of this wild resource, 4 novel
isoforms of its RIP (HmRIP) were purified and characterized. HmRIP
was stable to a broad range of temperature (0-65 °C) and pH
(3-9). Unlike all other type II RIPs, HmRIP1, 2 and 4 showed unique
sugar affinity for L-rhamnose, meso-inositol and L-arabinose besides
the galactose. Amino acid sequence of HmRIP determined by cDNA
cloning showed deletions at one of the two sugar-binding sites.
Crystal structure of HmRIP-sugar complex determined by X-ray crystallography
revealed a significantly different conformation of the 2y sugar-binding
pocket. Due to deletion of two critical residues forming wall
of the pocket, the site has become much broadened. Therefore the
sugar binds in a significantly different manner. The recognition
of the sugar chains present on the cell surface is the first step
in biological activity therefore HmRIP with distinct sugar specificity
has pharmacological significance.
P0478. Inflorescence morphology in Balanophoraceae: moving
in a twilight zone.
R. K. Eberwein;
Kärntner Botanikzentrum, Klagenfurt, Austria.
The pantropically distributed holo-and root-parasitic family Balanophoraceae
has panicled, mostly spadiceous inflorescence types with a remarkable
variety of different designs. Contrary to other authors, all inflorescences
are initiated endogenously in subterranean globose or sometimes
elongated tubers. Racemes (subfam. Mystropetaloideae, Helosidoideae
and Balanophoroideae), double racemes (subfam. Dactylanthoideae
and Lophophytoideae) and triple female racemes (subfam. Sarcophytoideae)
can be found. In tribe Helosieae spadices are covered by a dense
layer of hexagonal, umbrella like structures which could be identified
as bracts (not secondary axes as discussed before), showing an
up to now unknown and for leaves unusual developmental pathway
of peltation. Balanophoroideae possess spadices without secondary
branching (in tribe Langsdorffieae they are designed like Asteracean
heads). Structures covering the spadix, formerly described as
axes ("spadicelli"), turned out to be transformed bracts.
But it is still unclear if these "spadicelli" originate
from numerous individual bracts or few multiple splitted bracts.
13.8.1. Progress in Malpighiales phylogeny: new insights
from eight genes
K. J. Wurdack1, C. C. Davis2;
1Smithsonian Institution, Washington, DC, United States, 2Ecology
and Evolutionary Biology, University of Michigan Herbarium, Ann
Arbor, MI, United States.
Malpighiales include 29 families previously assigned to 13 different
orders sensu Cronquist. While the monophyly of most families within
the order has been established, interfamilial relationships are
largely unclear. Our phylogenetic analyses of DNA sequence data
from 8 genes (plastid atpB, matK, ndhF, and
rbcL; nuclear 18S and PHYC; and, mitochondrial nad1B-C
and matR) spanning nearly 120 malpighialean taxa is
beginning to resolve many of the major subclades within the order.
These data further support the recent addition of Rafflesiaceae
s.s. and Centroplacus, exclusion of Peridiscaceae, sister
relations of Elatinaceae+Malpighiaceae and Putranjivaceae+Lophopyxidaceae,
and inclusion of Paradrypetes in Rhizophoraceae s.l. New
findings show Podostemaceae apparently nested within Hypericaceae,
and a well-supported sister relationship between Phyllanthaceae
and Picrodendraceae. The implications of these new results for
the evolution of morphological characters, the problems of horizontal
gene transfer, and for biome evolution will be discussed.
1.7.1. Research on Orobanche: what do we know and
what should we get to know?
D. M. Joel;
Agricultural Research Organization, Ramat-Yishay, Israel.
Orobanche spp. (broomrapes) are parasitic plants that develop
multicellular haustoria, which connect to the roots of various
dicots. Their tiny seeds germinate only after perceiving a host
stimulus. Some species are weedy and cause severe damage to agriculture.
The globalization of these parasitic weeds, the evolution of new
races, and the gradual increase in their virulence pose threat
to many crops worldwide, while means to control them are scarce.
Studies of key developmental mechanisms of the parasitic interaction,
regarding germination, attachment, haustorium penetration and
host resistance, are needed for the understanding of their evolution.
Proteomics and genomics should provide data on the genes involved
in host-parasite interaction. Manipulation of developmental and
metabolic pathways, which are involved in the parasitic interaction
in both host and parasite, may provide protection against parasitic
weeds. New sources for resistance in host plants may also be developed,
employing specific antibodies, gene silencing, local release of
toxins, and false signals.
1.7.2. Molecular phylogenetics and taxonomy of Orobanche
s.l. (Orobanchaceae)
G. M. Schneeweiss1, J. Park1, J. Manen2, A. Colwell3;
1Institute of Botany, Vienna, Austria, 2Conservatoire et Jardin
Botaniques, Genéve, Switzerland, 3US Geological Survey,
Seattle, WA, United States.
Phylogenetic analyses of DNA-sequence data have greatly changed
our understanding of circumscription of Scrophulariaceae and allied
families, e.g., Orobanchaceae, traditionally comprising exclusively
holoparasitic taxa, now include both hemi- and holoparasitic members.
In a similar way, recent molecular phylogenetic analyses suggest
substantial re-definition of the genus Orobanche, which
is the largest of the holoparasitic genera in Orobanchaceae. One
group, with chromosome base number of x = 12, contains
the each monophyletic sections Gymnocaulis, Myzorrhiza,
and Trionychon. The second group, with chromosome base
number of x = 19, contains Diphelypaea and O.
sect. Orobanche, the latter again comprising three
distinct lineages. The relationships between these two major groups
and those to other genera are unclear. As already suggested by
previous authors, recognition of the sections of Orobanche
as separate genera would allow to better reflect the phylogenetic
patterns in a taxonomic system.
1.7.3. Orobanche-host plant interactions: ecological
and physiological aspects
J. A. C. Verkleij;
Institute of Ecological Science, Amsterdam, The Netherlands.
Among the various Orobanche species, a large difference
in host range exists from very small to extremely wide. Because
the Orobanche lifecycle is highly specialized for parasitism,
the first stages of host-parasitic interactions seemed to be essential
in determining host specificity. Orobanche seed germination
is dependent on several abiotic and biotic factors as shown in
various ecological and physiological studies. Although this first
stage can be considered as the most discriminating one in terms
of host selection, the germination process is too complex to draw
definitive conclusions. The next stages crucial for the development
of Orobanche are haustorium initiation, host tissue penetration
and physiological compatibility. Progress in understanding these
processes have been made in recent years using host plantparasite
model systems. After successful infection Orobanche relies
completely on its host for the supply of both reduced carbon,
nitrogen and also minerals. The response of the host to infection
by the holoparasite can be explained by just source -sink relations
and will be discussed with respect to other parasitic angiospermhost
systems.
1.7.4. Predictive empirical modelling of Orobanche
life cycle and seed ecology
A. J. Murdoch1, E. Kebreab2;
1The University of Reading, Reading, United Kingdom, 2The University
of Guelph, Guelph, ON, Canada.
Dormancy in Orobanche 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. 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 behaviour of the seed population. The
impact of these results is discussed for O. aegyptiaca parasitising
tomato.
1.7.5. Population genetics in Orobanche species
Z. Satovic1, D. M. Joel2, D. Rubiales3, J. Cubero4, B. Roman5;
1Faculty of Agriculture, Zagreb, Croatia, 2Newe-Ya'ar Research
Center, Agricultural Reserach Organization, Ramat-Yishay, Israel,
3IAS - CSIC, Cordoba, Spain, 4ETSIAM - UCO, Cordoba, Spain, 5IFAPA
- CIFA, Cordoba, Spain.
The studies of population genetics of Orobanche species
are of great importance since the understanding of the variability
within and between pathogenic populations is essential if selection
programmes need to target sources of resistance in different areas
and suitable breeding strategies need to be developed. The use
of morphological markers in Orobanche has been difficult
because holoparasitism resulted in a reduced number of suitable
characters even for taxonomical purposes. The distribution of
genetic variation in O. aegyptiaca, O. crenata,
O. cumana, O. foetida and O. ramosa populations
has been reviewed based on available molecular marker data. It
is shown that by using simple DNA marker systems (e.g. RAPDs and
ISSRs) the intraspecific variability can be assessed and problematic
issues such as the differentiation between botanical taxa, geographical
differentiation, and host-differentiation can be addressed.
1.7.6. Evolution of Ty1-copia and
Ty3-gypsy retroelements in holoparasitic Orobanche
(Orobanchaceae)
J. Park, G. M. Schneeweiss, H. Weiss-Schneeweiss;
Institute of Botany, University of Vienna, Vienna, Austria.
Retrotransposons (RTNs) are mobile genetic elements, which transpose
via an RNA intermediate. The transposition of RTNs is replicative,
i.e., the existing elements are not excised but the newly formed
copies re-integrate into new positions in the host genome. This
feature, among others, such as ubiquity and high copy number,
renders RTNs excellent molecular markers. We amplified and sequenced
rt gene of Ty1-copia and Ty3-gypsy RTNs (at
least 20 clones for each RTN type) from 13 Orobanche accessions.
These accessions are (i) the economically most important weeds
O. aegyptiaca and O. ramosa of sect. Trionychon
and O. cernua and O. crenata of sect. Orobanche,
and (ii) one close wild relative of each of these four taxa. While
in sect. Trionychon RTN diversity is higher with many small
unique RTN families, fewer RTN families are found in sect. Orobanche,
some of them comprising numerous and very similar rt sequences.
This suggests that species in sect. Orobanche might have
experienced a recent burst of RTN activity. Additionally, we found
indication of horizontal gene transfer for Ty1-copia and
Ty3-gypsy RTNs, both from sect. Trionychon to sect. Orobanche
and vice versa.
1.7.7. Orobanche species as weeds and
their management in sustainable agriculture
D. Rubiales1, M. Fernández-Aparicio1, B. Román2,
J. C. Sillero2, J. I. Cubero3;
1CSIC, Córdoba, Spain, 2IFAPA, Córdoba, Spain, 3UCO,
Córdoba, Spain.
About 3500 flowering plant species have lost their autotrophic
way of life during evolution and parasitise other plants in order
to supply themselves with water and nutrients. They are more than
a fascinating group of plants as a few of them are severe constraints
to major crops. By far the most economically damaging parasitic
weeds are members of the genera Striga (witchweeds) and
Orobanche (broomrapes). The most damaging Orobanche
species are O. crenata that causes huge damage to legume
crops, O. cumana that threatens sunflower, O. ramosa
that attacks potato, tobacco, tomato and hemp, and O. aegyptiaca
has very severe effects on legumes and vegetables, but also
other species might gain importance. The spread of these parasitic
weeds, and the gradual increase in their virulence pose threat
to many crops worldwide, while means to control them are scarce.
In the present work we revise their importance and re-evaluate
control methods in the light of recent developments in crop breeding
and molecular genetics.
3.12.5. Nutrients and heavy metal transfer from soil to
the host-hemiparastic plant association Cistus-Odontites luteus
growing on mine spoils
C. Poschenrieder1, A. Lombini1, M. Llugany1, E. Dinelli2,
J. Barcelo1;
1Universidad Autonoma de Barcelona, Bellaterra, Spain, 2Università
di Bologna, Bologna, Italy.
Odontites luteus (former Scrophulareaceae) a hemiparasitic
plant was found associated with Cistus species at mine
sites in Italy (Cu mine) and Catalonia (Pb, Ba mine). Soil, root
and shoot concentrations of selected mineral nutrients (Ca, Mg,
K, Fe, S, Mn, Zn, and Cu) and of non-essential elements (Al, Cd,
Pb, Ba, and Sr) were analysed in order to get a first picture
on how the hemiparasitic nutrient adquisition strategy may influence
the mobility of these elements. Cistus sp. restricted the
root to shoot transport of Cu, Zn, Al and Pb. In O. luteus
similar root and shoot concentrations of Cu and Zn suggest
that in this hemiparasitic plant the transport was less hampered,
probably due to a direct uptake of mobile metal species from either
or both xylem and symplastic sites of the host. In contrast, mobility
of Pb was restricted also in the hemiparasite. The host-hemiparasitic
plant association may serve as a model system for future investigations
on metal mobility as a function of metal speciation in plants.
Acknowledgement: Supported by DGICYT (BFU2004-02237CO2- 01) and
Plà Recerca Catalunya 2001 (SGR00200).
P1186. Host specialization in Orobanche foetida
M. M. Rojas1, D. Rubiales2, J. I. Cubero2, J. C. Sillero1;
1IFAPA-CIFA, Cordoba, Spain, 2IAS-CSIC, Cordoba, Spain.
Orobanche foetida is widely distributed in Mediterranean
area on wild legume plants, but has not been reported on cultivated
legume species, except on faba bean in Tunisia. A population of
O. foetida collected on Astragalus lusitanicus in
Spain and another population collected on faba bean in Tunisia
were studied to compare the pathogenicity on faba bean. The Spanish
population was no infective on faba bean and seeds were poorly
stimulated by all faba bean accessions. However, a substantial
proportion of geminated seeds were able to contact and start attachment
of faba bean roots, although failed to get established due to
a frequent hypersensitive like host root cells reaction. On the
contrary, the Tunisian population was very infective on faba bean
and seeds germinated profusely in all faba bean accessions, with
a higher success in attachment to faba bean roots and almost null
hypersensitive like reaction, resulting in a high establishment.
Some genotypic variation in resistance was observed in faba bean
germplasm. Resistance against O. crenata was not operative
against O. foetida, with the exception of cv. Baraca, the
most resistant to both species.
P1187. Evolution of phytochromes in parasitic Orobanchaceae
J. R. Bennett1, S. Mathews2;
1Natural History Museum, London, United Kingdom, 2Arnold Arboretum
of Harvard University, Cambridge, MA, United States.
The evolution of heterotrophy in plants may involve the evolution
of new morphological features such as haustoria, but there may
also be reduced selective pressure for the maintenance of features
associated with photosynthesis. Some developmental processes mediated
by phytochrome photoreceptors, such as leaf and chloroplast development
and the expression of photosynthetic genes are altered in parasitic
plants. Orobanchaceae contains both holoparasitic and hemiparasitic
species and so offers a system in which to investigate how the
functions of phytochromes might be altered in parasitic plants.
We have used DNA sequences of PHYA, the gene encoding phytochrome
A, to infer a phylogeny for the family. The well-supported gene
phylogeny suggests that at least some hemiparasites and holoparasites
have two copies of PHYA and that some PHYA genes
harbor novel introns. There is also evidence that PHYA sequences
are evolving under relaxed constraints and we are investigating
patterns of molecular evolution in more detail to determine whether
selective pressures change along branches to major clades or whether
they might be closely correlated with shifts in habit.
P1188. Genetic diversity in two variants of Orobanche
gracilis Sm. [var. gracilis and
var. deludens (Beck) A. Pujadas] from different
regions of Spain
B. Roman1, R. Hernandez2, A. Pujadas2, J. Cubero2, D. Rubiales3,
Z. Satovic4;
1IFAPA - CIFA, Cordoba, Spain, 2ETSIAM - UCO, Cordoba, Spain,
3IAS - CSIC, Cordoba, Spain, 4Faculty of Agriculture, Zagreb,
Croatia.
The pattern of genetic variation among populations of two taxa
of Orobanche gracilis Sm. [var. gracilis and var.
deludens (Beck) A. Pujadas] from Northern and Southern
Spain growing on different hosts was analysed using RAPD markers.
The Dice's distance matrix was analyzed by UPGMA method and the
resultant dendrogram clearly divided populations by region and
botanical variety with the Southern populations being more differentiated
among them in both cases (var. gracilis and var. deludens).
Concerning O. gracilis var. deludens, the dendrogram
has also shown host differentiation between populations growing
on two different species, Ulex baeticus and Ulex parviflorus.
A complementary analysis of principal coordinates (PCoA) confirmed
these results. The analysis of molecular variance (AMOVA) indicated
that the lowest level of differentiation was found among the Northern
O. gracilis var. gracilis populations whereas in
the case of O. gracilis var. deludens from the South
most of the genetic diversity was attributable to differences
among populations.
P1189. Hemiparasitism: a way station to holoparasitism or
an evolutionary stable strategy?
J. E. Armstrong;
Illinois State University, Normal, IL, United States.
Is hemiparasitism an evolutionary stable strategy (ESS) or just
a way station on the road from autotrophy to holoparasitism? Studies
on the obligate hemiparasite Pedicularis canadensis (Rhinanthaceae)
suggest that in prairie communities where nutrients or water are
very limiting factors, parasitism is an adaptation both for enhancing
acquisition of nutrients, particularly nitrogen, and/or water
and for enhancing photosynthesis, thus maintaining both systems.
The presence of the hemiparasite even enhances species diversity
by extracting a higher cost upon dominate species, like grasses,
in comparison to ephemerals like shooting star, Dodecatheon
meadia. This lousewort species also inhabits forest communities
in eastern North America where the prairie model predicts increased
gain via parasitism without enhancing photosynthesis. If so, the
lousewort's photosynthetic potential should decline in forest
communities shifting the balance toward holoparasitism.
P1190. Anatomical features of the stem structure in the
Orobanchaceae
E. O. Korol`kova;
Moscow State Open Pedagogical University, Moscow, Russian Federation.
All the of Orobanchaceae are parasitic plants without chlorophyll.
This family consists of nearly 225 species belonging to 16 genera.
The anatomical structure of the stem sin 87 species of 13 genera
has been studied. In connection with parasitic way of life this
plants have very simple morphological structure. Their anatomical
structure become more develop, especially their excretory system.
There are two excretory mechanisms ( by the glandular hairs in
Orobanche, and by the epidermal cells in Cistanche)
were found. As the anatomical data on stem structure shown, the
Orobanchaceae is a natural taxon that should not be regarded
as subfamily Orobanchoideae of the family Scrophulariaceae.
The taxonomic position of the genus Lathraea in Scrophulariaceae
is confirmed, however, by its stem anatomy. The diagnostic
value of some stem features of Orobanchaceae has been established.
The sections of genera Orobanche and Cistanche are
well distinguished by features of stem anatomical structure.
P1191. The Figwort Family (Scrophulariaceae Juss.) in Belarussian
Flora
M. A. Jus;
Belarussian State University, Minsk, Belarus.
Scrophulariaceae is one of the largest family of Angiosperm in
the temperate areas of the North hemisphere. The objects of our
investigation include aboriginal and synantropical components
of Scrophulariaceae (incl. Orobanchaceae Vent.) in Belarus. The
work comprises critical taxonomic revision of complex groups,
nomenclatural, caryological, ecological and phytocoenological
information about all species of Figwort family in this region,
with an issue of 8 years work of the author, with field experiences
and revision of more than 7 000 specimens of the herbaria KRAM,
KW, LE, LECB, LW, LWS, MHA, MSK, MSKU, MW, WIR etc. The phytogeography
of the Scrophulariaceae in this region is compared to the flora
in other neighbour areas (Poland, Baltic countries, adjacent regions
of the Ukraine and Russia). Among the main contributions in our
work are also presented an analytical key for the identification
of the taxa, dot maps of the distribution of the endangered, rare
and critical species, as well as information about protection
and sustainable use of representatives of the Figwort family in
Belarus.
P1192. Phenetic analyses of morphological traits in the
Alectra sessiliflora complex (Orobanchaceae)
J. J. Morawetz, A. D. Wolfe;
The Ohio State University, Columbus, OH, United States.
Alectra (Orobanchaceae) is a genus of primarily hemiparasitic
herbs. Alectra sessiliflora var. sessiliflora, var.
senegalensis and var. monticola form a morphologically
cohesive group with overlapping distributions throughout sub-Saharan
Africa, and are characterized by sessile yellow flowers and a
branching habit. Traditional characters used to distinguish varieties
were stamen filament pubescence or calyx pubescence. These characters
are degenerate, preventing confident placement of a single specimen
within one variety. This difficulty suggests that the taxonomic
delimitations may not be meaningful. A phenetic study was undertaken
to determine if this complex is best treated as a single large
polymorphic taxon, or as a series of similar yet discrete taxa.
Seventeen morphological characters were examined on 134 operational
taxonomic units (OTUs), and the data were analyzed using UPGMA,
PCA and discriminant analyses. Discrete clusters were not identified
by the analyses.
P0259. Cuscuta jalapensis parasite on Coffea arabica
in Veracruz, México
M. López-Curto1, C. Esquivel-Huesca1, D. Díaz-Pontones2,
J. Márquez-Guzmán1;
1Facultad de Ciencias. Universidad Nacional Autónoma de
México, Ciudad de México, Mexico, 2Ciencias de la
Salud. Universidad Autónoma Metropolitana, Ciudad de México,
Mexico.
Cuscuta jalapensis has been detected parasiting coffee
bean plants in Coatepec, Mexico. It is widely known that this
parasite affects productivity of different crops. Coffee culture
is quite important in Mexico so we decided to search how Cuscuta
stablishes in coffee plantations. How deeply goes the haustoria
into the host. What about the enzimatic mechanism of penetration.
We also studied the embryology of this plant; our goal was to
study some aspects of the biology of Cuscuta jalapensis and
its invasion strategies on coffee cultures. Samples in LRW resin
were sliced 2µm width for light microscope observations;
we observed haustoria at SEM and, we detected activity of peroxidase
enzime in 8µm cryostat slices, Sigma Immunochemicals technique.
This orange filiform herb invades coffee plants through herbs
and shrubs, on suitable hosts develops haustoria that penetrates
beyond vascular bundles reaching medula. We identify peroxidase
enzime involved in the generation of an entry pathway. We found
a high incidence of abortion and observe perennation and autoparasitism.
The only way to avoid infestation is to cut off infested plants
and eliminate herbs aside
P0606. Evolution of plastid genomes within the parasitic
flowering plant genus Cuscuta
K. Krause, S. Berg, K. Krupinska;
Institute of Botany, Kiel, Germany.
The holoparasitic plant genus Cuscuta comprises species
with full photosynthetic capacity, and functional chloroplasts,
achlorophyllous species and intermediate forms with restricted
photosynthetic activity and degenerated chloroplasts. Compared
to nonparasitic plants, extensive deletions have taken place in
the plastid DNA of achlorophyllous species encompassing photosynthetic
as well as regulative genes, while green species like C. reflexa
have retained most of the plastid genome. 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 intermediate species, 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. Thus, Cuscuta is an interesting
model for the evolution of reduced organellar genomes.
P1411. Phylogeny and plastid genome evolution in the parasitic
genus Cuscuta (Convolvulaceae)
S. Stefanovic1, R. G. Olmstead2;
1University of Toronto at Mississauga, Mississauga, ON, Canada,
2University of Washington, Seattle, WA, United States.
Previous findings on plastid (pt) genome structural rearrangements
in Cuscuta were attributed to its parasitic life style,
but without rigorous phylogenetic framework. Long PCR approach
was used to sequence nearly entire pt genome from poorly investigated
subgenus Grammica in order to determine its size, structure,
gene content, and synteny. This pt genome is compared to that
of tobacco and corresponding regions from taxa in the other Cuscuta
subgenera. When all known pt genome rearrangements in Convolvulaceae
are considered in a molecular phylogenetic framework three categories
of rearrangements in Cuscuta are revealed: plesiomorphic,
autapomorphic, and synapomorphic. Many of the changes in Cuscuta,
previously attributed to its parasitic mode of life are better
explained either as plesiomorphic conditions within the family,
i.e., conditions shared with the rest of the Convolvulaceae, or
in most cases, autapomorphies of particular Cuscuta taxa,
not shared with the rest of the species in the genus. The synapomorphic
rearrangements are most likely to correlate with the parasitic
lifestyle, because they represent changes found in Cuscuta
exclusively.
P2535. Combating Noxious Exotic Weed Mikania micrantha
in the Field
M. Li1, B. Wang2, B. Liu2, P. Yu2, H. Yu2, X. Cheng2, Q. Zan3,
Y. Wang2;
1National Key Laboratory of Biological Control, Sun Yatsen University,
Guangzhou, China, 2National Key Laboratory of Biological Control,
Sun Yatsen University, GUANGZHOU, China, 3Guangdong Neilingding
Futian National Nature Reserve, Shenzhen, China.
Mikania micrantha is a noxious alien weeds with a slightly
woody vine species belonging to Asteraceae. It was introduced
to Hong Kong as early as 1884 and now spread far beyong Hong Kong.
M. micrantha was able to use shrubs and small trees as
its support and then smothered the supports with thick mantels
of its shoots. Physical removal experiment showed that uprooting
all the creeping stems completely was difficult. The remained
creeping stems sprouted in a short time and some of the slashed
stems revived under considerable precipitation and the effect
could only maintain for several months. Sulfometuron methyl was
an effective herbisde to kill the weed. Cuscuta campestris,
a parasitic plant, was able to suppress of M. micrantha.
No other species was found to be dead caused by C. campestris
within the infected circle. Restructuring plant community
with multi species planting was conduct. Regional, fast growing,
broad canopy and tall tree were criteria for selecting plant species.
Within two years, the canopy of the community became continuous
and suppressed the underneath weed, especially M. micrantha,
indicating the effectiveness of the restoration measurement.
SIUC / College of Science / Parasitic Plant Connection
URL: http://www.parasiticplants.siu.edu/meetings/IBC2005.html
Last updated: 31-Jul-05 / dln