Soil temperatures and inoculation techniques affect emergence and reisolation of Sclerotinia sclerotiorum from soybean

Emergence of Amsoy soybean (Glycine max) seed inoculated withSclerotinia sclerotiorum was significantly reduced below noninoculated seed at soil temperatures of 25°, 30°, and 35 °C, but not at 20 °C.S. sclerotiorum was readily reisolated from wound-inoculated stems of seedlings and nearly mature plants above the point of inoculation and below to the crown area, but not from roots. The fungus was recovered from stems but not roots of 15-day seedlings grown in sterile soil before infestation of the soil surface with a suspension of mycelium and sclerotia and assayed at 15 days after soil infestation. When compared to healthy, seeds, infected seeds withS. sclerotiorum were characterized by appearing flattened.Supported in part by the Illinois Agricultural Experiment Station; Regional Project S-72; and U.S. Agency for International Development, grant csd-1922.