Morphological and Phylogenetic Evidence for Rhytidhysteron phayaoense sp. nov. (Hysteriaceae) From Northern Thailand

During a survey of saprobic fungi in Phayao Province, northern Thailand, a hysteriaceous ascomycete was collected from decaying twigs of Shorea obtusa . Multigene phylogenetic analyses based on LSU, ITS, SSU and tef1‐α sequence data resolved the new isolate within Rhytidhysteron . Morphologically, our specimen differs from the closely related taxa R. thailandicum , R. bannaense and R. sichuanense , particularly in characters of the sexual morph, including longer and strictly superficial ascomata (823–2816 µm), a thicker exciple (70–188 µm) and smaller ascospores (17–25 × 5–8 µm; L / W = 3.2). Asexual morphs have not been reported for R. bannaense or R. sichuanense . The asexual morph of our isolate differs from that of R. thailandicum in having larger conidiomata with elongate papillate necks (314–605 × 141–253 µm) and longer conidiogenous cells (7–10 µm long). Based on morphological characteristics and phylogenetic evidence, we introduce Rhytidhysteron phayaoense sp. nov. This study expands knowledge of Rhytidhysteron in Thailand and contributes to a better understanding of species diversity within the genus.