Abstract

Abstract Microdochium fungi are globally distributed and function as plant pathogens, saprobes, or endophytes, infecting a wide variety of plant hosts. In the present study, four novel Microdochium species collected from diseased leaves of Bambusoideae sp., Acronychia pedunculata, and Symplocos sumuntia in Hainan Province, China, were isolated, identified, and formally described. Species delimitation was achieved through a combination of molecular phylogenetic inference and morphological comparison with closely related taxa. Phylogenetic analyses were conducted on concatenated ITS, LSU, RPB2, and TUB2 sequence datasets using both maximum likelihood (ML) and Bayesian inference (BI) methods. The results demonstrate that these four species form well-supported, independent monophyletic lineages that are clearly distinct from all previously described Microdochium species. Morphological examination of colony characteristics, conidiogenous cells, and conidia further corroborates their taxonomic novelty by revealing consistent phenotypic differences from closely related species. Accordingly, four new species of Microdochium are proposed: M. acronychicola, M. brevisporum, M. chinense, and M. wuzhishanense.