Phialomyces koreanus sp. nov., A Novel Soil Fungus from Korea.

Abstract

Strain KNUF-23-295 was obtained from a soil sample collected from Nami-myeon, Geumsan-gun, Chungcheongnam-do Province, South Korea, during a survey of fungal diversity in Korean soils. Molecular analysis based on internal transcribed spacer (ITS) regions revealed 97.3% sequence similarity to Phialomyces macrosporus but comparatively lower similarities to other species in the genus Phialomyces, including P. humicoloides (94.6%) and P. arenicola (94.4%). These results suggest that the strain is phylogenetically affiliated with the genus Phialomyces. Furthermore, strain KNUF-23-295 exhibited distinct cultural and morphological characteristics that differentiated it from closely related species. It was characterized by the production of a pink pigment on potato dextrose agar, asymmetrical colonies on cornmeal agar, shorter and narrower conidiophores (6.5-20.0 × 2.5-3.9 μm), bottle-shaped phialides (8.4-20.9 × 2.0-4.7 μm), and a distinctive conidial arrangement consisting of solitary conidia, short chains (two to five), long chains (up to 15), and aggregates. Two phylogenetic trees based on a concatenated dataset of ITS, LSU, Cct8, and RPB2 sequences consistently placed strain KNUF-23-295 as a distinct and well-supported lineage in the genus Phialomyces, providing strong phylogenetic evidence for its novelty. The morphological characteristics and multilocus phylogenetic data indicate that strain KNUF-23-295 is a novel species, for which the name P. koreanus sp. nov. is proposed.