Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme IV: POPULATION DYNAMICS AND ECOLOGY Posters
maintained. All the three AM fungus species (Gigaspora
margarita, Glomus fasciculatum and Glomus mosseae)
used in experiment promoted the growth of cabbage
seedlings significantly. However, the level of the
promotion varied among the three species. These results
suggest that the existence of AM fungus in the rhizosphere
improves the soil condition for plant growth, and it
provides a new approach for the plant-AM fungus
symbiotic system.
929 - Interactive effects of nutrient applications and
arbuscular mychorrhizal colonization on little bluestem
grass (Schizachyrium scoparium)
H. Antonsen 1* , R.C. Anderson 2 , S.A. Juliano 2 & S.S.
Dhillion 1
1 Department of Biology and Nature Conservation,
Agricultural University of Norway, Postbox 5014, N-1432
Aas, Norway. - 2 Department of Biological Sciences, Illinois
State University, Campus box 4120, Normal, Illinois
61790-4120, U.S.A. - E-mail: hilde.antonsen@ibn.nlh.no
A manipulative field study was conducted in 1985 to
evaluate the impacts of supplemental nutrients (N, P, K and
Ca+Mg) on little bluestem grass (Schizachyrium
scoparium) with a high (20.2 ±1.6%) or low (2.6 ±0.7%)
level of colonization by arbuscular mycorrhizal fungi
(AMF). Low-colonized plants were grown in autoclaved
soil and outplanted into fumigated soil in the field, while
high-colonized plants were grown in unsterilized soil and
outplanted into unfumigated field soil. Originally, data
were analyzed by multiple univariate analyses of variance.
Previous conclusions drawn from these analyses were that
bases (Ca+Mg) were the limiting nutrients in this system.
A reanalysis of the data was performed by means of
multivariate statistics. New interpretations suggest that P
was the limiting nutrient in this system, since application of
P increased growth of S. scoparium when AMF
colonization was low. However, no effect of P application
on growth was found for plants with high levels of
colonization. This interaction is explained by the cost of
having a fungal partner. Thus, in this sand prairie system
AMF restricts growth of S. scoparium. In addition,
application of bases enhanced AMF colonization under
natural conditions.
930 - Phytopathological characteristics and
environmental impact on the different fungi of the
Gaeumannomyces/Phialophora (G/P) complex
C. Augustin * , K. Ulrich & A. Werner
ZALF, Dep. of Land Use Systems and Landscape Ecology,
Eberswalder Str. 84, D-15374 Muencheberg, Germany. -
E-mail: caugustin@zalf.de
The G/P complex contains fungi that cause take-all
diseases on cereals as well as apathogenic fungi. To study
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Book of Abstracts
the interactions of different groups, about 2000 isolates
from numerous geographic locations in Germany were
differentiated into species and varieties as well as on the
intravarietal level using RAPDs. Based on this strain
collection, the phytopathological behaviour of
representative isolates was evaluated on several cereal
varieties. Beside differences between species and varieties
we found a high variation in aggressiveness, especially to
wheat, among isolates of var. tritici. Whereas one RAPD
group of the var. tritici consisted exclusively of high
pathogenic isolates, the other one contained pathogenic,
apathogenic and even growth promoting isolates. In order
to predict the potential risk of take-all it is necessary to
analyse both the composition of the G/P fungi population
and the impact of different environmental factors on the
abundance of respective fungal groups. In our study we
monitored spatial occurrence and distribution of species,
varieties and subgroups of the G/P-complex as a function
of soil variables, weather conditions and crop rotation over
4 years. Data show that the various fungi analysed
displayed clearly different claims concerning
environmental factors. Actual weather and several soil
parameters were determined as the most important
discriminating influences. Results may provide a useful
basis for detailed improvement of prognostic models.
931 - The direct effect of nitrogen as a mechanism for
change in ectomycorrhizal fungal communities
P.G. Avis, D.J. McLaughlin * , I. Charvat & P. Reich
University of Minnesota, Plant Biological Sciences
Graduate Program, 220 Biosciences Center, 1445 Gortner
Avenue, St. Paul MN 55108, U.S.A. - E-mail:
davem@tc.umn.edu
The mechanisms causing shifts in ectomycorrhizal fungal
(EMF) communities exposed to increased nitrogen (N) by
atmospheric deposition or fertilization are not understood.
The effects of N increase could be direct, or could be due
to ancillary effects such as altered pH or a change in
limiting nutrients. This study examines the direct effects of
increased N by examining the response of EMF
communities to a 16-year fertilization experiment in an oak
savanna. The experiment consists of two levels of nitrogen
fertilization (5 and 17 g N m -2 yr -1 ) and unfertilized plots.
Each fertilization treatment also receives equal background
levels of P, K, Ca, Mg, and S added to offset ancillary
effects of N. Fertilization has increased soil N, held pH
constant and not caused limitation by other nutrients.
Meanwhile, fertilization 1) decreased the abundance of
aboveground EMF sporocarps for all species except
Russula amoenolens (which increased 7 fold); 2) held
belowground EMF richness constant as measured by
morphotype and PCR-RFLP methods; but 3) altered the
dominant fungi in the EMF communities: Unfertilized
EMF communities are dominated by species with extensive
external hyphae, notably Cortinarius species, while heavily
fertilized communities are dominated by those that lack
external hyphae, primarily R. amoenolens. These data show
that the direct effect of N addition may be the driving
mechanism behind the dramatic shifts in EMF communities
in ecosystems that experience N deposition.