Abstract
Pleurotus cornucopiae var. citrinopileatus protoplasts derived from a wild-type dikaryotic strain were irradiated with UV light to obtain mutants displaying sporulation-deficient (sporeless) phenotypes. From a total of 5,566 regenerated dikaryotic mycelia obtained after UV treatment, six were shown to be mutants with sporulation-deficient traits. Based on the survival rate, the suitable irradiation dose was estimated to be 19.0-24.7 mJ/cm^2. It was confirmed that five mutants maintained a sporulation-deficient phenotype after subculturing three times at intervals of approximately one week. Furthermore, it was presumed that three of the mutants had a sporeless trait that arose as a dominant mutation from one nucleus of the original dikaryotic strain. In contrast, one mutant had a dominant mutation in the other nucleus, but the defect in the one remaining mutant could not be determined. The mutants obtained at a high irradiation dose (24.7 mJ/cm^2) had a much lower spore germination rate than the other mutants. The sporeless mutants obtained from this study formed fewer than 0.1% of the number of spores formed by the wild strains.
