Phylogenetic assessment and taxonomic revision of Scytalidium (Helotiales, Leotiomycetes)

Members of <i>Scytalidium</i> are primarily saprotrophic and are known for their ability to colonize a variety of substrates, including soil, decaying plant material, and wood. During an investigation of soil microfungi in <i>Capsicum annuum</i> cultivation areas of China, seven <i>Scytalidium</i> isolates were obtained from soil samples collected in Guizhou. In this study, we revised the genus <i>Scytalidium</i> by combining morphological characteristics and phylogenetic analyses based on concatenated ITS-LSU sequences. The results showed that <i>Scytalidium</i> sensu stricto comprises 16 species, including the type species <i>S. lignicola</i> and four novel species proposed in this study (<i>S. chlamydosporum</i>, <i>S. guizhouense</i>, <i>S. rodionovae</i>, and <i>S. tongrenense</i>). Ten species were excluded, and six species were treated as uncertain due to the lack of available molecular sequences. This study revised the genus <i>Scytalidium</i>, expanded its species diversity and geographical distribution, and lays the foundation for future taxonomic research on this genus.