The genus Metarhizium Sorokīn 1879, a group of entomopathogenic fungi with a global distribution, comprises approximately 80 species that are adapted to diverse ecosystems [1]. Metarhizium is widely recognized as a biocontrol agent against insect pests, and offers an environmentally friendly alternative to chemical pesticides [2]. Although traditionally considered host are generalists with a cosmopolitan distribution, recent morphological and molecular analyses have suggested that these fungi are more host- or region-specific than previously thought [1,3]. These findings highlight the need for further studies to clarify their precise distribution and diversity. In South Korea, five Metarhizium species (M. anisopliae, M. guizhouense, M. marquandii, M. pemphigi, and M. rileyi) have been recorded [4], underscoring the potential unexplored diversity harbored in South Korea. In a recent survey of cicada-associated fungal communities, Metarhizium strains were isolated from cicadas (Cryptotympana atrata). In this study, we report the isolation of Metarhizium viridulum for the first time in South Korea, based on morphological and molecular analyses.

Cicada cadavers were collected from Miryang, South Korea (35°21’13.97″ N, 128°45’39.68″ E), in August 2023. Fungal strains were isolated from cadavers on potato dextrose agar (PDA; Difco, Becton Dickinson, MD, USA) at 25℃ and subcultured until pure cultures were obtained. All strains were deposited in the herbarium of Changwon National University (CWNU). For molecular analysis, genomic DNA was extracted from the strains using the AccuPrep Genomic DNA Extraction Kit (Bioneer, Daejeon, Korea). PCR amplification was performed using a SimpliAmp™ Thermal Cycler (Applied Biosystems, Waltham, MA, USA) for the nuclear ribosomal large subunit (LSU) region with LR0R [5] and LR5 primers [6]. Elongation factor 1-alpha (EF1a) was amplified using EF1-983F and EF1-2218R primers [7], following previously described protocols [8]. The PCR results were verified using 1% agarose gel electrophoresis, and the PCR products were sequenced using an ABI 3730xl Sequencer (Macrogen, Seoul, South Korea). Sequences were checked and assembled using MEGA5 [9] and aligned locus-specifically with reference sequences using MAFFT v.7 [10]. Because the M. viridulum type strain sequence is unavailable [11], the sequence of the authentic strain BCC36261, which has been morphologically and molecularly characterized [1], was used for molecular analysis. Maximum-likelihood (ML) phylogenetic analysis was performed with concatenated LSU and EF1a sequences using RAxML v.8 [12] with the GTRGAMMA model and 1000 bootstrap replicates. All sequences from this study have been deposited in GenBank (accession number PQ790513-14). Metarhizium strains CSC23C0001 and CSC23C0002 clustered monophyletically with the reference strain BCC36261 of M. viridulum, with 96% bootstrap support (Fig. 1). In both strains, pairwise comparisons with strain BCC36261 revealed sequence similarities of 100% and 99.77% in the LSU and EF1a region, respectively.