Book of Abstracts (PDF) - International Mycological Association

IMC7 Tuesday August 13th Lectures
176 - Taxonomic perspectives on some ascomycetous
endophytes of mycorrhizas
R.S. Currah
Department of Biological Sciences, University of Alberta,
Edmonton, Alberta, T6G 2E9, Canada. - E-mail:
r.currah@ualberta.ca
Roots are habitat for a wide variety of fungi including a
large number of ascomycetes. Several groups of
ascomycetous anamorphs consistently appear during
isolation protocols using traditional culturing methods or
where diversity estimates are made using DNA analyses.
Among the taxa recovered, Phialocephala fortinii,
Leptodontidium orchidicola, Scytalidium vaccinii and
similar species (teleomorphs apothecial or suspected as
such), Oidiodendron spp., and Geomyces pannorus
(teleomorphs cleistothecial) are frequent Leotiomycetes.
Other taxa include Heteroconium chaetospira and species
of Phialophora, Cladosporium, Phoma, and large numbers
of unidentified or partially characterized sterile taxa. In
most cases, the nature of the association between these
fungi and the host plant roots is unknown but their well
developed saprobic abilities suggest their role as mutualists
with plants is probably not mycorrhizal in the usual sense.
Continuing isolation work along with morphological,
enzymatic and molecular characterization, coupled with
resynthesis studies with host plants, will lead to a clearer
understanding of the niches occupied by these fungi in
roots and mycorrhizas.
177 - Non-mycorrhizal root endophytes - aspects on
their ecology
A. Jumpponen
Kansas State University, Division of Biology, Manhattan,
KS66506, U.S.A. - E-mail: ari@ksu.edu
Non-mycorrhizal root endophytes are a heterogeneous
group of fungi with possible beneficial associations with
their host plants. Recent data from a primary successional
sub-alpine ecosystem and a secondary successional
temperate grassland ecosystem suggest greater abundance
of non-mycorrhizal endophytes than mycorrhizal fungi.
The abundance of mycorrhizal and non-mycorrhizal, rootinhabiting
fungi may fluctuate according to physiology or
phenology of the host. Two competing hypotheses are
presented: 1) these fungi are parasitic and tap into the host
photosynthate translocation during seasonal changes in
host physiological activity, 2) these fungi are actively
involved in controlling host photosynthate reallocation. To
identify the dominant fungi in rhizosphere, a shotgun
cloning experiment was conducted using environmental
DNA from soil and rhizosphere samples. Fungi in the
shotgun cloned rDNA libraries represented ascomycetes,
basidiomycetes, chytridiomycetes and zygomycetes.
Detected fungal communities were concluded to be very
similar in soil and rhizosphere. This is interpreted to
indicate that root-inhabiting fungi frequently possess
extramatrical hyphae extending to the soil. Alternatively,
large proportion of the root and rhizosphere inhabiting
fungi are common soil fungi and facultatively colonize host
tissues. The potential of soil-inhabiting fungi having
biotrophic and/or endophytic phases will be discussed.
178 - Ectendomycorrhizas - specialized associations
between members of the Pinaceae and ascomycete fungi
R.L. Peterson
University of Guelph, Department of Botany, Guelph,
Ontario, Canada. - E-mail: lpeterso@uoguelph.ca
Ectendomycorrhizas (ECM) are formed in two genera,
Pinus and Larix, when roots are colonized by a few
ascomycetous fungal species, primarily Wilcoxina mikolae
and Wilcoxina rehmii. Two dematiaceous species and
Sphaerosporella brunnea have also been reported to form
ECM with these genera. Some of these fungi are capable of
forming typical ectomycorrhizas with other conifer genera
and with angiosperm species. Reports of other genera of
conifers and angiosperms possessing ECM are based on
field collections of roots of unknown age and thus may
represent senescing ectomycorrhizas. ECM are common in
Pinus and Larix seedlings in nurseries, regenerated
seedlings on degraded sites, and in some natural forest
sites. The identifying structural characteristics of ECM are
a limited mantle, an Hartig net, and intracellular hyphae
forming hyphal complexes. The latter form soon after
Hartig net development. Intracellular hyphal complexes
occur in epidermal and cortical cells and are surrounded by
host-derived plasma membrane and an interfacial matrix of
unknown composition. Although ultrastructural features of
the fungus-root cell interface suggest that these may be
sites of nutrient exchange, there is no evidence for this. It is
known that some of the fungi involved are able to
breakdown complex carbohydrates but carbon transfer to
young seedlings has not been demonstrated. Suggestions
have been made that ECM may be important in the
establishment of seedlings in harsh environments.
179 - Community structure and phylogeny of ericoid
and epacrid mycorrhizal fungi
S.M. Berch 1* , T.R. Allen 2 , M.L. Berbee 2 & C.B. McLean 3
1 Ministry of Forests Research Branch Laboratory, PO
9536, Victoria BC V8W 9C4, Canada. - 2 University of
British Columbia, Department of Botany, Vancouver BC
V6T 1Z4, Canada. - 3 University of Melbourne, Burnley
College, 500 Yarra Boulevard, Richmond, Victoria 3121,
Australia. - E-mail: shannon.berch@gems7.gov.bc.ca
To understand the community structure of ericoid
mycorrhizal fungi in the roots of ericaceous and
epacridaceous plants, researchers have cultured hundreds
of fungal isolates from thousands of mycorrhizal root
Book of Abstracts 57