Atractosporocybe, Leucocybe and Rhizocybe: three new clitocyboid genera in the Tricholomatoid clade (Agaricales) with notes on Clitocybe and Lepista.

A molecular multigene analysis (ITS, 18S and 28S nrLSU ribosomal DNA, tef1, rpb2) was used to support the proposition of three new genera of clitocyboid fungi. Leucocybe is proposed to accommodate the clade formed by Clitocybe connata and C. candicans. Clitocybe inornata is invested as type species of Atractosporocybe, while the new genus, Rhizocybe, is proposed for the former species of section Vernae of Clitocybe, C. vermicularis, C. pruinosa and C. rhizoides. The three lineages are related to the families Lyophyllaceae and Entolomataceae and independent from the Clitocybeae clade. Morphologically Rhizocybe is characterized by the presence of conspicuous rhizomorphs, while Atractosporocybe presents long fusiform spores. Leucocybe includes two whitish species in the former section Candicantes of Clitocybe, but no relevant shared characteristic feature was detected. Other whitish clitocyboid species, such as C. phyllophila (= C. cerussata), C. dealbata, C. rivulosa, and Singerocybe hydrogramma, are shown to be genetically related to the core lineage of the Clitocybeae.