Exploring the dominant endophytic pleosporalean fungi in <i>Poaceae</i> plants: taxonomic novelties within the suborder <i>Massarineae</i>

The suborder Massarineae, within the order Pleosporales (class Dothideomycetes), includes many fungi that act as dominant endophytes in Poaceae plants. However, despite recent advancements, the phylogeny and taxonomy of endophytic Massarineae remain insufficiently resolved. In this study, comprehensive phylogenetic and morphological analyses were conducted for two key families within Massarineae – Didymosphaeriaceae and Periconiaceae – by incorporating collections of novel endophytic strains from Poaceae hosts. Multilocus phylogenetic analyses revealed distinct clades in both families, leading to the proposal of 10 new taxa within Massarineae. Within Didymosphaeriaceae, two new genera (Proxiconiothyrium gen. nov. and Chlamydosphaeromyces gen. nov.) and three new species (Proxiconiothyrium yunnanense sp. nov., Neptunomyces yunnanensis sp. nov., and Chlamydosphaeromyces glomeratus sp. nov.) are described; for Periconiaceae, three new species (Periconia catenata sp. nov., P. neomacrospinosa sp. nov., P. longibrachiatum sp. nov.), one new combination (P. fueloephazae comb. nov.), and one new sensu stricto taxon (P. macrospinosa s.s.) are introduced. Detailed morphological descriptions are provided for each newly established taxon. The results significantly improve the taxonomic and phylogenetic framework for Massarineae endophytes and provide a valuable reference for exploring the diversity and evolutionary differentiation within other taxonomic groups of Pleosporales.