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Intraspecific Protoplast Fusion Between Auxotrophic Mutants of Rhizoctonia solani. T. Hashiba, National Institute of Agricultural Sciences, Yatabe, Ibaraki-ken 305, Japan; M. Yamada, National Institute of Agricultural Sciences, Yatabe, Ibaraki-ken 305, Japan. Phytopathology 74:398-401. Accepted for publication 23 September 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-398.

Auxotrophic mutants of Rhizoctonia solani isolate 131, from anastomosis group 1, were isolated by treatment of protoplasts with N-methyl-N' -nitro-N-nitrosoguanidine. Low-speed centrifugation of protoplast suspensions permitted separation of uninucleate and enucleate protoplasts from predominantly multinucleate protoplasts. Intraspecific protoplast fusion between auxotrophic mutants obtained from the uninucleate/enucleate fraction was induced by polyethylene glycol and Ca²⁺. The fused cells grew stably on minimal medium and produced sclerotia. Thus, the proposed method is expected to be useful for the isolation of auxotrophic mutants in multinucleate filamentous fungi which produce no spores on artificial media.