Morphological and Phylogenetic Characterization of Trichomerium koreanum sp. nov. and Exophiala radicis Belonging to Chaetothyriales Fungi in Korea

The order Chaetothyriales encompasses black yeasts and related fungi known for their diverse morphologies, asexual reproduction, and habitat preferences. In this study, we isolated two fungal strains belonging to Chaetothyriales, designated KNUF-23-13A and KNUF-22-020, from a longhorn beetle (Cyrtoclytus capra) and soil sample, respectively, in Korea. Phylogenetic analyses based on the concatenated nucleotide sequences of the internal transcribed spacer regions and partial sequences of the large subunit (LSU) rRNA, β-tubulin (TUB2), and actin (ACT) genes revealed that the strains were grouped with strains of Trichomerium and Exophiala, respectively. For strain KNUF-23-13A, cultural and morphological differences were observed in the shape and size of mycelium between it and its phylogenetically closest species, Trichomerium lapideum CGMCC 3.17311^T, supporting the novelty of this isolated species. In the case of strain KNUF-22-020, the cultural and morphological characteristics were similar to those previously reported for E. radicis P2854^T. Based on morphological and phylogenetic analyses, we revealed KNUF-23-13A as a novel species, which we describe and name T. koreanum sp. nov., and KNUF-22-020 as Exophiala radicis, a previously unreported species in Korea.