Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
26 - Genetic heterogeneity in Phialocephala fortinii
populations along a latitudinal transect
M.M. Piercey * , M.A. McPherson, S.W. Graham & R.S.
Currah
Dept. Biological Sciences, University of Alberta,
Edmonton, Alberta, T6G 2E9, Canada. - E-mail:
mpiercey@ualberta.ca
Dark septate root endophytes (DSE) commonly inhabit
roots of vascular plants in cold-stressed environments. One
species of DSE, Phialocephala fortinii, displays very little
host specificity and, when inoculated on some plants, a
variety of effects can be observed including an increase in
dry weight of the host plant, a decrease in dry weight of the
host plant, or no observed effect. The apparent strict
asexual mode of reproduction would indicate that there
should be minimal variation in this fungus within a
population, with distinct clones occupying distinct habitats.
To assess whether genetic variation within P. fortinii is
correlated to latitude and how this variation is structured
within and among populations, P. fortinii was isolated from
Salix root fragments collected from 40 x 40 m plots along a
latitudinal transect from 49°N to 78°N. Genetic
heterogeneity of isolated P. fortinii strains was evaluated
by amplified fragment length polymorphism (AFLP)
analysis and comparisons were made within populations
and between populations. Clones were not detected within
any population, and at all latitudes a single, distinct
individual was found inhabiting each collected Salix root
fragment. Genetically distinct populations were detected
only in arctic latitudes.
27 - Mechanisms and factors implicated in genet
distribution and in dynamics of populations of
ectomycorrhizal basidiomycetes
H. Gryta
CESAC, 29, rue Jeanne Marvig 31055 TOULOUSE Cedex
4, France. - E-mail: gryta@ecolog.cnrs.fr
Among ectomycorrhizal fungi -root symbionts of woody
plants-, Basidiomycetes are the most diversified (with
about 4500 described species) and studied ones. In natural
environments, roots of woody plants are potentially
connected to an assemblage of several fungal species each
represented by more or less different individuals. To
understand the functioning and ecological roles of
ectomycorrhizal fungi, a frequent approach is to focus on
local populations of these fungi to determine their genetic
diversity and its distribution. This to subsequently infer
how biotic and abiotic processes and determinants lead or
not to establishment of fungal individuals, to their
persistence as growing mycelia and, finally, to temporal
changes in fungal populations. Contrasting with the
strongly discussed but more often conserved sporophores
sampling method, the constant development of molecular
markers in the last twelve years has largely contributed to
great advances in this approach. Accurate characterizations
of populations have revealed large variations of
demographic strategies (often defined as the relative parts
of sexual reproduction and of vegetative growth in
structuring a population) among species as well as between
populations sampled in different environments of a done
species. Advances and comments concerning this approach
are illustrated with examples from works using Tricholoma
populinum, Tricholoma scalpturatum, Hebeloma
cylindrosporum and Suillus variegatus as models.
28 - Global patterns of genetic variation in
Schizophyllum commune
T.Y. James * , J.-M. Moncalvo & R. Vilgalys
Department of Biology, Duke University, Durham, NC
27708, U.S.A. - E-mail: tyj2@duke.edu
Some mushroom species can be noticeably common and
have wide geographic distributions. One such species is the
wood decaying split-gill mushroom Schizophyllum
commune. Our initial study addressed the global population
structure of S. commune and asked whether long distance
spore dispersal could possibly explain the fungus'
distribution and occurrence. Earlier studies by John Raper
demonstrated that the global population is completely
interbreeding, and more surprisingly that the many matingtypes
are randomly distributed with regard to climate and
geography. Using both allozyme and DNA markers, we
demonstrated that S. commune is in fact divisible into three
highly divergent geographic lineages: South America,
North America, and the Eastern Hemisphere. Evidence for
even smaller scale population substructure has been
observed among isolated populations in the Caribbean.
Through a selective spore-trapping method, we found that
spores of S. commune are extremely common in the air
flora, yet extant populations are genetically subdivided,
perhaps arguing for a role in natural selection in
maintenance of population differentiation. Finally, direct
studies of the mating-type genes themselves suggest an
explanation for Raper's observation of mating-type
distribution is the prolonged maintenance of all possible
mating-types within each geographic lineage through
strong balancing selection.
29 - Chemical organization of the Aspergillus fumigatus
cell wall and a revisited role for GPI-anchor proteins in
cell wall organization
I. Mouyna, T. Fontaine, M. Bernard, S. Chabane & J.P.
Latgé *
Unité des Aspergillus, Institut Pasteur, Paris, France. - Email:
jplatge@pasteur.fr
Recent structural analysis of covalent linkages between the
different constitutive polysaccharides of the structural
alkali-insoluble skeleton of the cell wall of Aspergillus
Book of Abstracts 11