Selection and characterization of crystalviolet-and malachite-green-resistant mutants in Volvariella volvacea.

Volvariella volvacea, the straw mushroom, has long been considered as a primary homothallic species. However, great variations in monosporous isolates have ralsed a considerable debate on the sexuality pattern of this edible Basidiomycete fungus. Because clamp connection is absent in V. volvacea, the production of genetically marked strains offers a possible means of resolving this problem. In this study, ultraviolet irradiation of basidiospores and mycellal fragments was used to induce crystal-violet- and malachite-green-resistant mutants. Cross-resistance to crystal violet and malachite green occurred between both classes of mutant. The difficulties of inducing mutants in this multinucleate fungus and the significance of mutant markers are discussed.