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.

Trichoderma spp. are globally distributed and are considered significant fungal resources. This study presents the discovery of 11 new species of Trichoderma: T. caeruleum, T. gongcheniae, T. graminicola, T. graminis, T. hongkuii, T. parapeberdyi, T. neoguizhouense, T. neohongkuii, T. parahamatum, T. parahongkuii, and T. shaanxiensis. All of these new species were isolated from soils, except for T. caeruleum, T. graminicola, T. graminis, and T. neohongkuii, which were found as endophytes in Poaceae plants. The phylogenetic position of these novel species was determined by analysing the concatenated sequences of the second largest nuclear RNA polymerase subunit encoding gene (rpb2) and the translation elongation factor 1-alpha encoding gene (tef1). The results of the phylogenetic analysis revealed that each new species formed a distinct lineage: T. gongcheniae, T. graminicola, T. graminis, T. neoguizhouense, T. parapeberdyi, and T. shaanxiensis belong to the Harzianum Clade, T. hongkuii, T. parahongkuii, and T. neohongkuii are new members of the Koningii Clade, T. parahamatum belongs to the Hamatum Clade, and T. caeruleum does not fall within any of the named clades. The study also provided a detailed description of the morphology and cultural characteristics of the newly discovered Trichoderma species. The discovery contributes to the advancement of knowledge about Trichoderma species resources in China.