Asexually reproducing fungi play a significant role in essential processes in managed and wild ecosystems such as nutrients cycling and multitrophic interactions. A large number of such taxa are among the most notorious plant and animal pathogens. In addition, they have a key role in food production, biotechnology and medicine. Taxa without or rare sexual reproduction are distinguished based on their sporulating structures and conidiomata in traditional morphology-based taxonomy. The number, variation and diversity of asexually reproducing taxa are insufficiently known, even though fungi capable of asexual reproduction may provide an untapped, rich biological resource for future exploitation. Currently, ca. 30,000 asexual species belonging to ca. 3800 genera have been reported (including 1388 coelomycetous and 2265 hyphomycetous genera). Recent reports (2017–2020) reiterate that the number of asexually producing fungi is higher than the number of frequently sexually-reproducing fungi. With the advent of molecular tools and the abandonment of the dual nomenclature system for pleomorphic fungi, priority criteria were established and revisited in the latest outline of fungi and fungus-like taxa. However, species numbers and taxonomic boundaries of pleomorphic taxa and their synanamorphs or synasexual morphs have yet to be addressed. The number of species of speciose genera (e.g. Alternaria, Aspergillus, Cercospora, Fusarium, Phoma and Pseudocercospora), cryptic species, species of pleomorphic genera, less studied life modes (such as lichenicolous taxa, taxa from extreme environments) and species from biodiversity-rich areas still need evaluation to achieve more reliable estimates of their diversity. This paper discusses the current knowledge on the matter, with diversity estimates, and potential obstacles in several chapters on (1) speciose genera; (2) pleomorphic genera; (3) cryptic species; (4) well-studied but insufficiently resolved taxa, e.g. leaf inhabiting species, marine fungi, (5) less studied life modes, e.g. lichenicolous, rock-inhabiting fungi, insect-associated and yeast-forming taxa and (6) species from biodiversity-rich areas.

Plant debris are habitats favoring survival and multiplication of various microbial species. During continuing mycological surveys of saprobic microfungi from plant debris in Yunnan Province, China, several Corynespora-like and Dendryphiopsis-like isolates were collected from dead branches of unidentified perennial dicotyledonous plants. Four barcodes, i.e., ITS, LSU, SSU and tef1-α, were amplified and sequenced. Morphological studies and multigene phylogenetic analyses by maximum likelihood and Bayesian inference revealed three new Corynespora species (C. mengsongensis sp. nov., C. nabanheensis sp. nov. and C. yunnanensis sp. nov.) and a new Kirschsteiniothelia species (K. nabanheensis sp. nov.) within Dothideomycetes, Ascomycota. A list of identified and accepted species of Corynespora with major morphological features, host information and locality was compiled. This work improves the knowledge of species diversity of Corynespora and Kirschsteiniothelia in Yunnan Province, China.

Plants play an important role in maintaining the ecological balance of the biosphere, but often suffer from pathogenic fungi during growth. During our continuing mycological surveys of plant pathogens from terrestrial plants in Jiangxi and Yunnan provinces, China, 24 strains of Pestalotiopsis isolated from diseased and healthy tissues of plant leaves represented eight new species, viz. P. alpinicola, P. camelliicola, P. cyclosora, P. eriobotryae, P. gardeniae, P. hederae, P. machiliana and P. mangifericola. Multi-locus (ITS, tef1-α and tub2) phylogenetic analyses were performed using maximum-likelihood and Bayesian inference to reveal their taxonomic placement within Pestalotiopsis. Both molecular phylogenetic analyses and morphological comparisons supported them as eight independent taxa within Pestalotiopsis. Illustrations and descriptions of these eight taxa were provided, in conjunction with comparisons with closely related taxa in the genus. This work highlights the large potential for new fungal species associated with diseased plant leaves.

Three new species of Distoseptispora, viz. D. mengsongensis, D. nabanheensis, and D. sinensis, are described and illustrated from specimens collected on dead branches of unidentified plants in Yunnan Province, China. Phylogenetic analyses of LSU, ITS, and TEF1 sequence data, using maximum-likelihood (ML) and Bayesian inference (BI), reveal the taxonomic placement of D. mengsongensis, D. nabanheensis, and D. sinensis within Distoseptispora. Both morphological observations and molecular phylogenetic analyses supported D. mengsongensis, D. nabanheensis, and D. sinensis as three new taxa. To extend our knowledge of the diversity of Distoseptispora-like taxa, a list of recognized species of Distoseptispora with major morphological features, habitat, host, and locality is also provided.