Morphological and Phylogenetic Characterization of <i>Raffaelea xyleboricola</i> sp. nov. from <i>Xyleborus</i> Beetles in Korea

A fungal isolate was obtained from ambrosia beetles (<i>Xyleborus</i> sp.) collected using beetle traps placed in an apple orchard in Gunwi-gun, Daegu, Republic of Korea. Cytochrome oxidase I (COI) gene sequencing confirmed that the beetles belonged to the genus <i>Xyleborus</i>. The fungal isolate, designated ARI-25-A12, was subjected to morphological and molecular identification and characterization. On malt extract agar (MEA), colonies exhibited a white, fur-like surface, and hyphae penetrated the medium along the margins. As the colony matured, the center became dull yellow, and after 20 days of incubation, the colony diameter reached 49.6-56.0 mm. Morphologically, conidiophores were hyaline, simple or occasionally branched, and conidia were hyaline, thin-walled, unicellular, and globose. Conidia produced yeast-like sprout cells through a budding-like process, and the average conidial size was 5.2 × 5.2 μm (<i>n</i> = 100). Molecular phylogenetic analyses based on ITS, LSU, SSU, and β-TUB gene sequences indicated that ARI-25-A12 is classified within the genus <i>Raffaelea</i>. Phylogenetic trees constructed from ITS sequences and a combined dataset of LSU, SSU, and β-TUB gene sequences consistently classified the isolate as a distinct lineage, clearly separated from previously reported <i>Raffaelea</i> species, with additional morphological differences supporting its distinct classification. Based on these results, ARI-25-A12 is described herein as <i>Raffaelea xyleboricola</i> sp. nov.