Colletotrichum macroconidii sp. nov. and six new records of Colletotrichum (Glomerellaceae, Glomerellales) from southwestern China

<i>Colletotrichum</i>, a genus in the phylum Ascomycota and the family Glomerellaceae, is globally recognized as a significant plant pathogen affecting various hosts. In this study, 31 <i>Colletotrichum</i> strains were isolated from plant hosts in southwestern China, specifically from Guizhou and Yunnan Provinces. Phylogenetic and morphological analyses revealed one novel species, <i>Colletotrichum macroconidii</i> <b>sp. nov.</b>, and 11 previously known species. Six of these species represent new host and regional records: <i>C. fioriniae</i>, <i>C. trichellum</i>, <i>C. juglandicola</i>, <i>C. nanhuaense</i>, <i>C. jiangxiense</i>, and <i>C. magnum</i>, in addition to five known species: <i>C. nymphaeae</i>, <i>C. metake</i>, <i>C. fructicola</i>, <i>C. siamense</i>, and <i>C. gloeosporioides</i>. Multilocus phylogenetic analyses placed strains of <i>C. jiangxiense</i> in a well-supported clade with <i>C. nullisetosum</i>, <i>C. oblongisporum</i>, <i>C. gracile</i>, and <i>C. tengchongense</i>, which are here treated as synonyms due to their nomenclatural invalidity, morphological overlap, and phylogenetic evidence. Similarly, <i>C. speciosum</i> and <i>C. simulanticitri</i> clustered with <i>C. nymphaeae</i> and are synonymized with it based on insignificant genetic divergence and invalid nomenclatural status. Species identification was conducted using a comprehensive approach that combined multilocus phylogenetic analysis with detailed morphological characterization. This expanded dataset significantly contributes to our understanding of the genetic diversity and ecological distribution of <i>Colletotrichum</i> in southwestern China.