Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
81 - Mycorrhizal fungi in wetlands: the role of the
extramatrical mycelium
A.V. Rice 1* , M.N. Thormann 1 , B.J. Wilson 1 , H.D. Addy 2 &
R.S. Currah 1
1 Department of Biological Sciences, University of Alberta,
CW-405, Edmonton, AB T6G 2E9, Canada. - 2 Department
of Biological Sciences, University of Calgary, 2500
University Drive, N. W., Calgary, AB T2N 1N4, Canada. -
E-mail: arice@ualberta.ca
Wetland plants are generally considered non-mycorrhizal
but recent surveys have confirmed that mycorrhizal fungi
are common in wetland plants and that all of the usual
types (VAM, orchid, ericoid, and ectomycorrhizas along
with dark septate endophytes) can be found in appropriate
host species. Among these fungi, we are interested
primarily in the ascomycetous associates if peatland plants
that have dematiaceous hyphae, a group that includes
Phialocephala fortinii (DSE) and Oidiodendron maius
(ericoid), among others. Phialocephala fortinii is a
dematiaceous hyphomycete common in the roots of a
variety of wetland plants. The ecological role of P. fortinii
is poorly understood but it is an enzymatically diverse
species, capable of degrading various organic nitrogen (N)
and carbon (C) sources, including complex phenolic
polymers, such as lignin, that are important constituents of
peat. In many acidic bogs, P. fortinii is absent from the
roots of ericaceous shrubs where Oidiodendron maius is
the most frequent isolate. Our research demonstrates that
O. maius is also an enzymatically diverse species, capable
of utilizing organic C and N, and a proficient decomposer
of Sphagnum fuscum, the primary component of bog peat.
Our research suggests that the extramatrical mycelium of
selected mycorrhizal fungi and other root endophytes may
be important in nutrient cycling within wetland habitats.
82 - Diversity of mycorrhizas in wet ecosystems, what
we should consider: from a case study on alder EM to a
new approach to screen AM
F. Buscot 1* , C. Renker 1 , K. Pritsch 2 & J.-C. Munch 2
1 University of Jena, Institute of Ecology, Dornburger
Strasse 159, D-07743 Jena, Germany. - 2 GSF-Research
Center for Environment and Health GmbH, Insitute of Soil
Ecology, Neuherberg, D-85758 Oberschleissheim,
Germany. - E-mail: francois.buscot@uni-jena.de
The mycorrhizal status in wet ecosystems is complex,
including non truly mycorrhizal associations with dark
septate fungi to plants like poplars or alders forming both
AM and EM. In the latter case, the scarce available results
indicate that AM presence decreases and EM diversity
increases from wet pioneer to dryer advanced succession
phases. The aim of the paper is to present partial results
and new technical developments on the basis of which
exhaustive studies of the mycorrhizal status in wet
ecosystems could be performed. A first point concerns a
comparison between above and below ground diversity of
EM at two sites of an alder forest near a lake in Northern
Germany. By combining identification of fruiting bodies,
morphotyping of the EM and analysis of the polymorphism
in the ITS region of both kinds of samples, it was possible
to demonstrate an increase of the EM diversity from the
lake to the higher site of the stand. Direct investigations of
AM diversity in the field are difficult for technical reasons.
Identification on the basis of the spore morphology is
possible, but spores only partially reflect the diversity of
the AM themselves. AM anatomy is not convenient to
determine the fungal partners at the 'species' level. Several
methods based on molecular biology have been proposed,
but the analyses are often hampered by contaminating
fungi. We have developed an approach combining a Nested
PCR with a restriction, which partially resolves the
difficulty.
83 - Contributions of arbuscular mycorrhizal fungi to
plant performance in wet ecosystems: studies with
Lythrum salicaria
K.J. Stevens * , S.W. Spender, R.L. Peterson & R.J. Reader
Department of Botany, University of Guelph, Guelph,
Ontario, N1G 2W1, Canada. - E-mail:
kjsteven@uoguelph.ca
The impact of arbuscular mycorrhizal (AM) fungi on plant
performance in wetland areas was investigated through
studies on Lythrum salicaria (L.). Under field conditions
plant performance and AM colonization levels varied with
water availability and there was a negative correlation
between plant performance and AM colonization levels.
Partially submerged plants produce numerous, free-floating
adventitious roots along submerged stem lengths. The
adventitious roots, the primary root system, and AM fungal
hyphae represent three possible pathways for resource
acquisition. We tested the hypothesis that, to sustain shoot
growth, a reduction in the ability of one or more pathways
to acquire resources will require an increase in resource
uptake in the remaining pathway(s). While greenhouse
studies revealed that individually AM fungi did not have a
significant effect on plant performance, the results did
indicate a relationship among the three pathways
supporting our hypothesis. Greenhouse studies were
conducted to determine if, in inundated soils, AM fungi
contribute to plant performance across a range of
phosphorus availabilities. AM fungi did not enhance
growth in inundated soils; in some cases performance was
limited and it is unlikely that AM fungi enhance
phosphorus nutrition in inundated soils. We suggest that
because of the large differences between terrestrial and
aquatic habitats, AM fungi may be performing different
roles in each habitat.
Book of Abstracts 27