Description of a new species of Gerhardtia (Lyophyllaceae, Agaricales) from Japan based on morphological and molecular phylogenetic analyses and live culture characteristics.

We describe a new species of Gerhardtia from Japan based on basidiomata morphology, live culture characteristics, and molecular phylogenetic analyses. Gerhardtia venosolamellata is found on broad-leaf litter, and is characterized by tricholomatoid to marasmioid basidiomata, an off-white to pale salmon-pink pileus surface with faint marginal striae, subdistant lamellae with lateral veins, a tomentose to strigose stipe base with hyphal strands generating arthroconidia measuring 4-7 × 2-3 µm, cyanophilic, elongate-ellipsoid to cylindrical, slightly verrucose or undulate basidiospores measuring 4.5-6 × 2.5-3 µm, and cyanophilic basidia measuring 25-35 × 5-6 µm and containing siderophilous granules. Phylogenetic analyses based on the internal transcribed spacer and large subunit regions of the fungal nrDNA indicates that G. venosolamellata is related to G. sinensis and G. highlandensis, but differs from the former with respect to basidiomata color, basidiospore shape, and habitat. An isotype specimen of G. highlandensis exhibited relatively close lamellae without veins, and slightly larger basidiospores (4.5-6.5 × 2.5-3 µm). Cultured mycelia of G. venosolamellata produced arthroconidia measuring 4.5-8.5 × 2.5-3 µm with both schizolytic and rhexolytic secession on MA and PDA media, and chlamydospores occasionally covered with crystals on MA and MYG media.