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Etiology

Pathogenicity of Some Select Soilborne Dematiaceous Hyphomycetes on Germinating Seed of Festuca rubra. James P. Madsen, Graduate research assistant, Department of Horticulture, Iowa State University, Ames 50011; Clinton F. Hodges, professor of horticulture and of botany and plant pathology, Department of Horticulture, Iowa State University, Ames 50011. Phytopathology 70:21-25. Accepted for publication 9 June 1979. Copyright 1980 The American Phytopathological Society.. DOI: 10.1094/Phyto-70-21.

The pathogenicity of Drechslera sorokinia, Curvularia geniculata, and Alternaria alternata, alone or in combination, to germinating seed and emerging seedlings of Festuca 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. Curvularia 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, however, was below that in response to either organism alone which suggested a synergistic pathogenic interaction between the organisms. Alternaria 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.