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Ecology and Epidemiology

Induction of Suppressiveness to Rhizoctonia solani in Soil. 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 70:994-998. Accepted for publication 10 April 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-994.

When soil was infested with large (>589 μm) propagules of Rhizoctonia solani, soil suppressiveness to R. solani was generated only in acidified or naturally acidic soils after replanting radish, alfalfa, or sugar beet at weekly intervals. As suppressiveness increased, the propagule density of Trichoderma harzianum also increased. Acidic pH levels enhanced in vitro growth of T. harzianum more than that of R. solani and stimulated its conidiophore formation and spore germination. The mechanism of antagonism was found to be parasitism followed by lysis rather than antibiosis; the fungus released active β-(1-3) glucanase and chitinase when grown on R. solani cell walls and lysed both living mycelium and cell walls of that fungus. In raw soil, T. harzianum also controlled damping-off of radish.