Polyclonal antisera were raised against cell walls of a soil aggregating basidiomycete isolated in eastern Montana (isolate BB1) which has been identified as a member of the russuloid clade using molecular genetic techniques. In cross-reactivity tests using quantitative enzyme-linked immunosorbent assay (ELISA), polyclonal antisera to BB I cross-reacted significantly with fungal species representative of the russuloid clade and little or no reactivity was observed with fungal species of the polyporoid, euagaric, hymenochaetoid, bolete and gomphoid-phalloid clades of the Homobasidiomycetes. These results suggested that the cell walls of fungal species from the russuloid clade share common antigenic binding sites that are recognizable by the polyclonal antibodies and that these sites were not found or were present in small amounts in fungal species from the other clades. Experiments on the water stability of artificial aggregates amended with fungal species representative of these six homobasidiomycete clades indicated that many species of the russuloid clade were very efficient soil stabilizers. Fungal species from the other clades vary in their ability to aggregate soil particles but cross-react weakly with the antibodies. ELISA was used on water stable aggregates (WSA) from soil samples of three dryland locations under conventional tillage, no tillage and fallow management practices and on WSA from soil samples from grass barrier strips that were undisturbed for 30 years. Greater antigenic response was observed from WSA of undisturbed soils compared to cultivated soils and from WSA of soils under no till compared to till or fallow management practices. These results suggested that specific soil aggregating russuloids in WSA are sensitive to soil disturbance such as tillage. To our knowledge, this study is the first report of the detection and quantification of a taxonomic group of specific soil aggregating Homobasidiomycetes in dryland soils under diverse agricultural systems.
