Uncovering hidden diversity in Didymellaceae from Yunnan: Introducing three novel species of Didymella and Nothophoma

Ascomycete diversity in Yunnan Province, China, remains substantially underexplored. Many species likely remain undetected. This study aimed to discover the ascomycete diversity in Yunnan, China, depending on three fungal collections obtained from Baoshan and Kunming city regions. Based on morphological characteristics, host association, ecological habitats, and multi-locus phylogenetic analyses of these collections, together with representative strains of taxa in Didymella and Nothophoma , three new species are introduced, namely Didymella baoshanensis , Nothophoma aceris , and N. ginkgonis . Phylogenetic analyses of a concatenated ITS, LSU, rpb2 , and tub2 sequence dataset using maximum likelihood and Bayesian inference methods supported the novelty of these taxa within Didymella and Nothophoma . Phylogenetically, D. baoshanensis forms a distinct sister lineage to the type strain of D. brevipilosa , with strong statistical support. Nothophoma aceris clusters with the invalidly published name N. juglandis with high support values. While N. ginkgonis forms a distinct branch as basal of N. ferruginea , N. platycladi , and N. pruni . Didymella baoshanensis was found as a saprobe on dead fern rachises and is characterized by multi-loculate ascostromata; subglobose to ampulliform, ostiolate ascomata; 8-spored, bitunicate, fissitunicate, cylindrical to subcylindrical-clavate asci embedded in broadly cellular pseudoparaphyses; and fusiform, hyaline, 1-septate ascospores. Nothophoma aceris was found as a saprobe on dead aerial twigs of Acer palmatum and is characterized by scattered to clustered, globose to subglobose, stromatic, brown to dark brown, glabrous, ostiolate, apapillate, pycnidial conidiomata; holoblastic, phialidic conidiogenous cells, sometimes proliferating at the same level, with 1–2 conidiogenous loci; and hyaline to brown or dark brown, subglobose, ovoid to obovoid, aseptate, thick- and smooth-walled conidia. Nothophoma ginkgonis was found as a saprobe on dead aerial twigs of Ginkgo biloba and is characterized by subglobose to hemispherical or ellipsoidal, uni-loculate, brown to dark brown, glabrous, ostiolate, apapillate, pycnidial conidiomata; holoblastic, phialidic, hyaline, ampulliform to somewhat isodiametric, unbranched, determinate, discrete, smooth-walled conidiogenous cells; and hyaline to light brown, or yellowish-brown, subglobose to ellipsoidal, or obovoid, aseptate, smooth-walled conidia. Detailed description, photographic illustration, and updated phylogenetic analyses of Didymella and Nothophoma are provided in the present study.