New genera and species of coniferous twig-inhabiting Rhytismatales from China.

Species in the order Rhytismatales M.E. Barr ex Minter (Leotiomycetes, Ascomycota) develop on a wide range of host plants, but prefer conifers, such as species of Cupressaceae and Pinaceae. Conifers, the largest group of gymnosperms, show a high diversity in China. In this study, the species diversity of Rhytismatales on twigs of conifers is investigated based on specimens newly collected in China. Morphological characteristics combined with multi-gene phylogenetic analysis (ITS, nrLSU, and mtSSU rDNA) revealed 18 new species, belonging to six new genera (Abiomyces, Cryptococcomyces, Labivalidus, Neotherrya, Pseudococcomyces, and Stipamyces) and three known genera (Hypoderma, Hypohelion, and Tryblidiopsis). Additionally, seven new combinations are proposed. The findings underscore the complexity of fungal taxonomy within Rhytismatales and the importance of considering multiple criteria for accurate classification. The study also explores the importance of host specificity for genus and species delimitation within the order. A key to genera and species of Rhytismatales on twigs of conifers worldwide is provided.