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.

The genetic relatedness among thirty-three natural isolates of an edible mushroom, Pleurotus ostreatus, collected from Japan, Europe, U.S.A. and Korea was characterized by isoelectric focusing on polyacrylamide gels. The activities of acid phosphatase, alcohol dehydrogenase, esterase, laccase and malate dehydrogenase displayed 19, 9, 32, 11 and 10 distinct isozyme patterns, respectively.By combining the isozyme patterns obtained with the five enzymes, every isolate showed its own distinct electrophoretic phenotype. A distance matrix calculated between all pairs of the 33 electrophoretic phenotypes based on the presence or absence of isozyme bands was analyzed by the group-average method. Results of the cluster analysis assigned the 33 phenotypes into four major groups, each of which coincided with geographically distinct populations. These results suggest that geographical distance between natural populations of P. ostreatus is correlated with the genetic divergence.