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Ecology and Epidemiology

Isolation and Biocontrol Potential of Trichoderma hamatum from Soil Naturally Suppressive to Rhizoctonia solani. Ilan Chet, Professor, Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Rehovot, Israel; Ralph Baker, professor, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523. Phytopathology 71:286-290. Accepted for publication 17 July 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-286.

A soil that appeared to be naturally suppressive to Rhizoctonia solani was collected from Columbia, South America. Suppressiveness was confirmed in the laboratory by comparing its conducive index (0.2) to that of a conducive Fort Collins clay loam (0.85). R. solani propagules repeatedly were added to both soils and the resultant disease incidence on radishes grown in the suppressive soil was lower (P = 0.01) than in comparable inoculations in the conducive Fort Collins clay loam. The Colombian soil contained 108 propagules of fungi per gram of which 8 105 propagules per gram was Trichoderma hamatum. When conidia of this fungus were placed in Fort Collins clay loam at 106 propagules per gram, the soil became suppressive to R. solani. T. hamatum attacked the mycelium of R. solani when the two microorganisms were grown in two-membered culture. It also produced the cell wall degrading enzymes β-(1-3) glucanase and chitinase, but there was no detectable antibiotic activity in vitro when T. hamatum was added to conducive Fort Collins clay loam at 106 conidia per gram soil. It became suppressive to R. solani not only on radishes, but on beans as well. Such treatment also induced suppressiveness to Pythium spp. attacking peas, and Sclerotium rolfsii in beans.

Additional keywords: antagonism, mycoparasitism, lysis, soilborne plant pathogens.