Phylogenetic position of Pholiota nameko in the genus Pholiota inferred from restriction analysis of ribosomal DNA

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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.