Dedikaryotization causing flat sectors in the dikaryotic mycelia of Pholiota nameko was investigated at different temperatures. Flat sectors appeared in the colonies of the most stocks at a high temperature (30℃) whereas they did not at lower temperatures. Therefore, the high temperature environment is considered to be one of the causes that promote dedikaryotization in the mycelial colony. The successively subcultured stocks showed increase frequencies of dedikaryotization even at a low temperature (25℃) as compared with the colonies with less subculturing.

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To characterize the commercial strains of F. velutipes, 14 wild isolates and 12 cultivated strains were examined for the RFLP of mitochondria DNA (mtDNA), its presence and the copy numbers of mitochondrial plasmids. All of the cultivated strains contained two species of linear plasmid DNA that are designated as pFV1 (8.3 kb) and pFV2 (8.9kb). Five strains out of 14 wild isolates contained mitochondrial plasmid. Among this five, three contained pFV2 and one contained the two plasmids together as the commercial strains. Only one isolate was found to harbor pFV1 alone. The copy number of mitochondrial plasmid in the current commercial strains is 15 to 40, which is 3 to 8 times that of the wild strains. When mtDNA of wild F. velutipes was cut with the restriction enzyme BglII, it showed RFLP irrelevant of its geographical origin. Wild strains were divided into three groups according to its RFLP. On the other hand, no polymorphism was found among the mtDNA of the cultivated strains. However, a specific mtDNA fragment, which hybridized with pFV1 in the Southern hybridization, was identified. pFV2 did not hybridize with mtDNA of either the cultivated or the wild strains.

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Aspergillus oryzae, Pediococcus halophilus and Saccharomyces rouxii are the main microorganisms used to make miso, because these microbes have a potent ability to produce amylase and protease, lactate dehydrogenase, and alcohol dehydrogenase, respectively. Recently, we discovered that some genera of mushroom also produces amylase, protease, lactate dehydrogenase and alcohol dehydrogenase. In this study we made a miso-like food using a mushroom in place of A. oryzae, P. halophilus and S. rouxii, and found that the miso-like food made using Pleurotus eryngii showed thrombosis preventing activity. There was a prolonged thrombin clotting time of 6.2 fold that of control.

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The genetic constitution of A and B incompatibility factors in five species of Pleurotus mushrooms was surveyed by linkage analysis. The B incompatibility factor recombinants from monospore isolates of P. citrinopileatus, P. cornucopiae, P. eryngii, P. ostreatus and P. sajor-caju were found. It was also demonstrated that the genetic distances between two subunits of the B incompatibility factor in these mushrooms, Bα and Bβ, were widely varied between 0 and 18.2 cM among the test strains. On the other hand, we could not isolate any A recombinants among about three hundred monospore isolates from either one of the six test strains of Pleurotus mushrooms. There was no linkage between the A and Bincompatibility factors in the test fungi as similar to various tetrapolar basidiomycetous mushrooms.

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