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Relevance of Mycoparasitism in the Biological Control of Rhizoctonia solani by Gliocladium virens. C. R. Howell, Research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Southern Crops Research Laboratory, P.O. Drawer JF, College Station, TX 77841; Phytopathology 77:992-994. Accepted for publication 26 November 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-992.

Conidia of two strains of Gliocladium virens that were strongly parasitic to Rhizoctonia solani were irradiated with ultraviolet light and screened for mycoparasitism in dual culture with R. solani. Three mutants that showed no mycoparasitic activity were isolated from each strain. The selected mutants retained the same antibiotic complement as the parent strains. Peat moss-Czapek’s broth cultures of parent and mutant strains had similar efficacy as biocontrol agents of cotton seedling disease induced by R. solani and as antagonists of sclerotia of R. solani in soil. These results indicate that mycoparasitism is not a major mechanism in the biological control of R. solani-incited seedling disease by G. virens.

Additional keywords: cotton, mutation, seedling disease.