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Fungistasis of Sclerotia of Sclerotium oryzae. R. Keim, Department of Plant Pathology, University of California, Davis 95616, Present address of senior author: Superintendent, South Coast Field Station, 7601 Irvine Blvd., Santa Ana, California 92705; R. K. Webster, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 65:283-287. Accepted for publication 30 September 1974. DOI: 10.1094/Phyto-65-283.

Sclerotia of Sclerotium oryzae germinate readily on distilled water, but not in rice-field soil. Soil inhibition of sclerotial germination apparently can only be effected by the presence of living cellular organisms, because it can be annulled by filtration (0.45 µm), heat sterilization, or by a 7-day period of soil microbial inactivity (dry at 1 C). Certain bacteria, actinomycetes, or fungi were found to produce inhibitory substances when incubated on potato-dextrose agar, while bacteria were found to do so apparently with only a substrate of sclerotial exudate. Organisms from a field soil with disease-free rice caused inhibition of sclerotial germination of higher magnitude than those from field soil endemic with stem rot disease of rice.