Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme IV: POPULATION DYNAMICS AND ECOLOGY Posters
considered that C. militaris has homothallism. For this
entomopathogenic fungus, homothallism is thought to be
effective character for producing stromata against rare
chance to encounter host insects.
1033 - Some saprobic fungi from Typha and their
competitive interactions on leaves
M.J. Schulz 1* , M.N. Thormann 1 , E.A. Smreciu 2 & R.S.
Currah 1
1 University of Alberta, Dept. of Biological Sciences,
Edmonton, AB T6G 2E9, Canada. - 2 Wild Rose Consulting,
Inc., 15109 77th Ave, Edmonton AB T5R 3B5, Canada. - Email:
mkschulz@hotmail.com
Typha latifolia is a major detritus producer in many
wetlands. A diverse group of fungi decompose this matter,
but how they work to partition the substrate spatially and
chemically is unknown. Psathyrella typhae, Talaromyces
ucrainicus, Hymenoscyphus repandus, H. scutula,
Hymenopsis typhae, Phoma sp., Cladosporium herbarum
and Sclerotium cf. hydrophilum were isolated from Typha
leaves at various stages of decomposition, and their
enzymatic abilities tested using a suite of in vitro tests.
Corresponding mass loss determinations using natural
substrate showed little correlation for many species,
indicating in vitro tests may not accurately represent
decompositional abilities in vivo. We also looked at
competitive interactions between two common saprobes
from T. latifolia, P. typhae and Sclerotium cf.
hydrophylum, by using differential morphology
(presence/absence of clamps, hyphal diameter) and
enzymatic abilities (pH tolerance and ability to acidify
casamino acid medium) to disinguish their relative
development in co-inoculated Typha leaf fragments. Even
though Sclerotium grew faster, P. typhae was the superior
competitor, able to inhibit and invade substrate already
colonized by Sclerotium.
1034 - From orchids (Neottia nidus-avis) to forest tree
roots: the mycorrhizal web of the Sebacinaceae
(heterobasidiomycetous 'Rhizoctonia')
M.-A. Selosse 1* , M. Weiß 2 , R. Bauer 2 & A. Tillier 1
1 Institut de Systématique (IFR CNRS 1541) du Muséum, 43
rue Cuvier, F-75005 Paris, France. - 2 Botanisches Institut,
Universität Tübingen, Auf der Morgenstelle 1, D-72076
Tübingen, Germany.
Mycoheterotrophic (MH) plants are achlorophyllous
organisms fed by fungi. Up to now, only
homobasidiomycetous ectomycorrhizal fungi have been
found in MH plants, while several MH orchids are
probably associated to Rhizoctonias,
heterobasidiomycetous fungi that are often parasitic or
saprobic. We investigated the MH Neottia nidus-avis, a
European orchid supposedly associated to a fungus of the
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Book of Abstracts
Rhizoctonia complex. 61 Neottia root systems were
analysed by amplification and sequencing of the fungal
rDNA, showing a specific association to a subclade of
Sebacinaceae. Ectomycorrhizae (ECM) growing near
Neottia roots were shown, through rDNA sequencing, to be
also colonized by the sebacinoid associates of the orchid
(83% of the typed ECM). Additional data suggests that the
same genets colonize the Neottia and neighbouring tree
roots. Neottia therefore confirms the emerging features of
MH plants, specifically associated with tree-colonizing
fungi. Up to now, available data did not exclude that
sebacinoids are saprobic or mycoparasites on ECM. Our
TEM analysis shows that they form typical ECM, with
dolipore ultrastructure supporting the molecular
identification of the fungus. Sequencing of the rDNA ITS
of the host plant showed that sebacinoids are not treespecific,
colonizing Carpinus, Fagus, Quercus, Tilia, etc.
This, together with some GenBank data, suggests that
Sebacinaceae is an overlooked mycorrhizal family, where
many species await morphological description.
1035 - Rare mechanism of genetic recombination in
Pleurotus ostreatus natural populations
A.V. Shnyreva
Department of Mycology & Algology, Faculty of Biology,
Moscow State University, Vorob'yevy Gory, Moscow
119992, Russia. - E-mail: shnyreva@herba.msu.ru
The higher basidiomycete fungi form panmictic
populations resulting from haploid progeny hybridization.
However, a dikaryon is also capable of contributing
fertilizing nuclei to a haploid monokaryon resulting in a
new dikaryon. Little is known about occurring diploidhaploid
mating in nature due to rather difficulties in
observing such phenomenon. Having analysed Pleurotus
ostreatus population structure, we have revealed rather rare
mechanism of genetic recombination via di-mon-mating in
a local population. We have analysed a sample of
heterokaryotic isolates collected within a log. All the
heterokaryotic isolates within an individual substrate were
somatically compatible and identical at 12 polymorphic
isozyme loci. To examine distribution of mating
incompatibility factors among basidiocarps within a single
fruit body cluster on a log, matings between their
monospore offspring were carried out. Some of the
dikaryons were identically constituted with respect to A
and B factors resulted in 25% of compatible pairings, while
the others were distinguished at one of the two mating loci
(75% of compatible pairings). This can be explained by
occurring diploid-haploid hybridization. Dikaryotic
individual occupying the substrate fuses with alien
monospore germling that leads to random combination of
three types of nuclei in cells of different basidiocarps
within a fruit body cluster. Data on population
structure,reproductive strategy will be also presented.
RFBR grant 01-04-49447.