Molecular phylogeny and morphology reveal four new wood-inhabiting fungi of Asterostroma and Radulomyces (Basidiomycota) from Southwestern China

In the ecosystem, wood-inhabiting fungi play an indispensable role in wood degradation and the cycle of substances. They are regarded as the "key player" in the process of wood decomposition because of their ability to produce various enzymes that break down woody lignin, cellulose, and hemicellulose. In this study, four new wood-inhabiting fungal species, Asterostromaparamuscicola, Radulomycesbambusinus, R.fissuratus, and R.sinensis, were collected from southwestern China and were proposed based on the morphological and molecular evidence. Asterostromaparamuscicola is characterised by the felted-membranous to pellicular basidiomata with pinkish to slightly salmon-buff, a smooth hymenial surface, a monomitic hyphal system, and generative hyphae bearing simple-septate and subglobose, thin-walled, echinulate basidiospores measuring as 8-8.8 × 7-8 µm. Radulomycesbambusinus is characterised by the resupinate basidiomata with pinkish-white to pink, a tuberculate hymenial surface, a monomitic hyphal system and generative hyphae bearing clamp connections, and subglobose, slightly thick-walled, smooth basidiospores measuring as 6-7.5 × 5.5-7.3 µm. Radulomycesfissuratus is characterised by the coriaceous basidiomata with grey to grey-buff, a tuberculate hymenial surface, a monomitic hyphal system and generative hyphae bearing clamp connections, and globose, slightly thick-walled, smooth basidiospores measuring as 7-9.5 × 6.5-8.5 µm. Radulomycessinensis is characterised by the coriaceous basidiomata with straw to cinnamon to ocherous, a tuberculate hymenial surface, a monomitic hyphal system and generative hyphae bearing clamp connections, and broadly ellipsoid, slightly thick-walled, smooth basidiospores measuring as 7.5-9 × 6.2-7.5 µm. Sequences of the internal transcribed spacer (ITS) and large subunit (nrLSU) markers of the studied samples were generated, and phylogenetic analyses were performed with maximum likelihood, maximum parsimony, and Bayesian inference methods. Phylogenetic analyses of ITS+nrLSU nuclear RNA gene regions showed that four new species were assigned to the genera Asterostroma and Radulomyces. The phylogenetic tree inferred from the ITS sequences revealed that A.paramuscicola was closely associated with A.macrosporum and A.muscicola. Based on the ITS sequences, the topology showed that Radulomycesbambusinus was retrieved as a sister to R.zixishanensis. The taxon R.fissuratus forms a monophyletic lineage. The other one species, R.sinensis, was closely associated with R.molaris and R.yunnanensis.