Pathogenicity of Some Select Soilborne Dematiaceous Hyphomycetes on Germinating Seed ofFestuca rubra

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Abstract
The pathogenicity of Drechslera sorokiniana, Curvularia geniculata and Alternaria alternata, alone or in combination, to germinating seed and emerging seedlings of F. rubra was evaluated. Seed inoculation and soil and seed infestation methods with D. sorokiniana reduced the amount and rate of seedling emergence and increased seedling mortality. C. geniculata reduced seedling emergence, but had no effect on rate of emergence or on seedling mortality. Pathogenicity of both organisms generally was greater in autoclaved soil than in nonautoclaved soil. These observations confirmed the pathogenicity of D. sorokiniana and established C. geniculata as a potentially important pathogen of germinating seed of F. rubra. Seedling emergence in soil infested with the combination of D. sorokiniana + C. geniculata was greater than that in response to either organism alone, which suggested competition between the organisms in the soil environment. Seedling emergence from seed infested with the combination of D. sorokiniana + C. geniculata was below that in response to either organism alone, which suggested a synergistic pathogenic interaction between the organisms. A. alternata had no consistent effect on seedling emergence or on seedling mortality, and it was not a pathogen. The combination of A. alternata with D. sorokiniana neither enhanced nor inhibited the pathogenicity of D. sorokiniana. The interaction of C. geniculata + A. alternata on seedling emergence was erratic, but suggestive of potential interactions that could inhibit or enhance the pathogenicity of C. geniculata.