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.

A large number of spores from fruiting bodies can lead to allergic reactions and other problems during the cultivation of edible mushrooms, including Pleurotus eryngii (DC.) Quél. A cultivar harboring a sporulation-deficient (sporeless) mutation would be useful for preventing these problems, but traditional breeding requires extensive time and labor. In this study, using a sporeless P. eryngii strain, we constructed a genetic linkage map to introduce a molecular breeding program like marker-assisted selection. Based on the segregation of 294 amplified fragment length polymorphism markers, two mating type factors, and the sporeless trait, the linkage map consisted of 11 linkage groups with a total length of 837.2 centimorgans (cM). The gene region responsible for the sporeless trait was located in linkage group IX with 32 amplified fragment length polymorphism markers and the B mating type factor. We also identified eight markers closely linked (within 1.2 cM) to the sporeless locus using bulked-segregant analysis-based amplified fragment length polymorphism. One such amplified fragment length polymorphism marker was converted into two sequence-tagged site markers, SD488-I and SD488-II. Using 14 wild isolates, sequence-tagged site analysis indicated the potential usefulness of the combination of two sequence-tagged site markers in cross-breeding of the sporeless strain. It also suggested that a map constructed for P. eryngii has adequate accuracy for marker-assisted selection.

This study characterized the genetic relationships in the natural population of Pholiota nameko (Strophariaceae) from Japan based on the RFLPs of two regions of nuclear rDNA (ITS and IGS) and mitochondrial DNA and the RAPD profile of nuclear DNA. No intraspecific polymorphism in rDNA was found among 36 isolates of P. nameko used. By contrast, digests of mtDNAs by endonucleases HindIII and BglII produced RFLP patterns that distinguished all isolates except for 2, and clustered 36 wild isolates phenetically into three major similarity groups. However, these groups as obtained by analysis of mtDNA RFLPs did not reflect the geographic origin of the isolates. In RAPD analysis of nuclear DNA using three kinds of primers, every isolate showed its own distinct RAPD profile, but all isolates were clustered only into a large similarity group by phylogenetic analysis based on the RAPD profile. From these results, it is suggested that wild isolates of P. nameko distributed in Japan form a continuous genetic population that has conserved the genetic diversity.

To estimate the phylogenetic position of Pholiota nameko in the genus Pholiota, restriction fragment length polymorphisms (RFLPs) for PCR products of 26S ribosomal RNA gene (rDNA), internal transcribed spacers (ITS), and intergenic spacer (IGS) of the rDNA repeat from P. nameko and eight of its closely related species were investigated, and a phylogenetic tree was constructed based on data that resulted from RFLP analysis. P. nameko was clustered together with P. adiposa, P. limonella, and P. aurivella of the subgenus Pholiota (section Adiposae). However, P. nameko and P. albocrenulata, both of which belong to the subgenus Hemipholiota, were phylogenetically separated from each other. Our results suggested that P. nameko is closely related to the members of the section Adiposae. Furthermore, the phylogenetic distance between this section Adiposae group including P. nameko and Kuehneromyces mutabillis was smaller than that between P. malicola var. macropoda of the subgenus Flammula and the members of section Adiposae. Our data indicate that molecular information on rDNA will be useful to reconstruct taxa within the genus Pholiota in the family Strophariacea that have been classified mostly on the basis of morphological characters.

Changes in contents of soluble low molecular weight carbohydrates and chitin in a sawdust-rice bran medium during mycelial growth of Pleurotus ostreatus in bottle cultivation were examined in relation to fruit-body yield of nine stocks. Glucose, mannitol, inositol, sucrose, and trehalose were detected in cultures after mycelial spreading. No significant correlation was observed between contents of soluble low molecular weight carbohydrate during mycelial growth and the fruit-body yield. Negative correlation was found between trehalose content in post-harvest cultures and the fruitbody yield. Chitin content in cultures decreased in the fruiting stage. Positive correlation was detected between chitin content of fruit-bodies and the decrement of chitin in post-harvest culture caused by fruit-body growth.