Search

To obtain a homothallic mutant in Lentinula edodes, basidiospores derived from the common Bmut dikaryon (A1B1mut × A2B1mut) were treated with UV irradiation. Of a total of approximately 5000 monosporous cultures recovered, a single basidiospore isolate was found to produce the hyphae bearing clamp connections without mating. This mutant strain could form fruit bodies, and all its single basidiospore isolates developed into colonies with clamp connections. Such homothallic behaviors were transmitted from the mutant strain to the next generation. During the germination and following hyphal elongation in a single basidiospore of mutant strain, clamp connections were clearly detected in multicellular hyphae, which contained two nuclei in each cell. Their clamp connections were morphologically variable, viz., pseudo, abnormal, and true clamps. Amplified fragment length polymorphism (AFLP) profiles among the basidiospore isolates of mutant strain were identical, indicating that the mutant strain produced isogenic basidiospore progeny.

A sporeless mutant dikaryon, completely defective in sporulation, was isolated from mycelial protoplasts of Pleurotus eryngii mutagenized by UV irradiation. Newly established dikaryons between one component monokaryon from the mutant, and 12 different wild type monokaryons from 3 other wild type dikaryons, all exhibited the sporeless phenotype, whereas those between the other monokaryon and the same wild type monokaryons all produced normal fruiting bodies. These results indicated that the sporeless mutation was induced in one of two nuclei of the mutant and was dominant. In the wild type basidia, the pattern of nuclear behavior during sporulation corresponded to the pattern C nuclear behavior as defined by Duncan and Galbraith. Cytological observation revealed that in the sporeless mutant meiosis was blocked at the meta-anaphase I in most basidia and hence basidiospores and sterigmata were not produced. Although fruiting bodies of the sporeless mutant showed a somewhat leaning growth, their gross morphology and its fruiting body productivity were comparable to that of the original wild type strain. Based on these results, it was considered that the sporeless mutant could serve as a potential material in breeding of sporeless P. eryngii commercial strains.

B incompatibility factor mutants (Bmut) in Pleurotus ostreatus were recovered from common-B mating heterokaryons resulted from matings between wild-type monokaryons with different A but the same B factors (A1B2 and A2B2) after NTG mutagenesis. The mutant monokaryons such as A1B2mut and A2B2mut were observed to have regularly uninucleated hyphal cells and to be compatible with each other. Matings between A1B2mut and A2B2mut monokaryons produced stable heterokaryons (A1B2mut + A2B2mut) that had binucleated hyphal cells with true clamp connections and formed normal fruit-bodies. Mating tests using basidiospore progeny from each of these heterokaryons revealed the bipolar mating pattern. Genetic analysis suggested that the mutation of B factor in P. ostreatus might occur in the B incompatibility factor genes.

A bacterial disease occurred on fruiting bodies ofLentinula edodes that formed outdoors onQuercus bedlogs during winter. The pathogen was identified asPseudomonas tolaasii based on morphological and bacteriological characteristics. Symptoms exhibited by infected fruiting bodies ranged from mild browning to severe necrotic cavities that characteristically developed in the cap tissue along the periphery of the attachment area to the stalk. The mode of symptom development was greatly influenced by the internal tissue structure of fruiting bodies. Multiplication of bacterial cells within the fruiting bodies was strictly intercellular and thus differed from previously reported bacterial disease ofL. edodes incited by an unidentified rod-shaped bacterium. The present strain ofP. tolaasii was capable of attacking theL. edodes mycelium in the inner bark and outer sapwood regions and caused lysis of heavily infected hyphae.