Abstract
Four mating-type monokaryons, A1B1, A1B2, A2B1, and A2B2, were screened from basidiospore clones of one Pleurotus salmoneostramineus fruit body. Auxotrophic strains were induced by irradiating the monokaryotic protoplasts with ultraviolet light, and they were mated with each other to obtain active basidiospore clones with appropriate combinations of auxotrophy and mating-type. The auxotrophic protoplasts were fused in polyethyleneglycol solution between the four kinds of mating-types, A≠B≠, A≠B=, A=B≠, and A=B=. The frequencies of fusant colony formation by the four kinds of combinations were all similar, independent of mating-type combinations. Heterokaryotic conformation of all four kinds of fusant mycelia were confirmed by the heterogeneity of nutritional requirements of the re-protoplasted clones of fusants. Prototrophy of A≠B≠ and A≠B= fusants was stable in a complete medium, but those of A=B≠ and A=B= fusants could be preserved only in a minimal medium. Clamp structures were observed in A≠B≠ and A≠B= fusants, but not in A=B≠ and A=B= fusants.
