Diversity of pathogenic ascomycetes on ancient Platycladus orientalis in Beijing based on multigene phylogeny and morphology

Ancient Platycladus orientalis is a precious heritage with significant historical, cultural, ecological, and landscape value. Under urban environmental stress and tree aging, diseases of ancient P. orientalis in Beijing have become increasingly severe; however, little is known about the diversity of these fungal pathogens. In this study, symptomatic samples were collected from 15 parks or temples in Beijing, from which a total of 56 fungal taxa were isolated from the interfaces between diseased and healthy tissues. Based on pathogenicity assays, multigene phylogenetic analysis and morphological observation, 45 ascomycete species, belonging to six orders, eight families, and 17 genera, were confirmed as the pathogens of P. orientalis , exhibiting varying levels of virulence. Among these, five species are described as new to science, namely Curvularia platycladi , C. platycladicola , Epicoccum platycladi , Fusarium beijingensis , and Toxicocladosporium quinquagintatreanum , and 30 species are new host records. This study establishes a foundational framework for future research on disease diagnosis and risk assessment in ancient trees.