First Report of Schizothyrium emperorae and S. wisconsinense Associated with Flyspeck on Apple in Korea

In August 2023, apple fruits exhibiting flyspeck signs were collected from orchards in Cheongsong-gun and Muju-gun, located in the Gyeongbuk and Jeonbuk provinces, during an investigation of apple diseases. Eleven fungal strains were isolated from the flyspeck signs on these apple fruits. To observe the cultural and morphological characteristics, the isolated fungal strains were cultured on potato dextrose agar, malt extract agar, and oatmeal agar at 25℃ in the dark for 2 weeks. Subsequently, conidia, conidiophores, and conidiogenous cells of the strains were examined. Internal transcribed spacer regions, translation elongation factor 1-α, and β-tubulin genes of the isolated strains were amplified for phylogenetic analysis. Based on cultural and morphological characteristics, alongside phylogenetic analysis, the strains were identified as Schizothyrium emperorae, S. pomi, and S. wisconsinense, respectively. The pathogenicity test confirmed that flyspeck symptoms were exhibited on inoculated apple fruits. In a previous study, Peltaster fructicola was reported to be the causal agent of sooty blotch and flyspeck disease in apples in Korea. To our knowledge, this is the first report of flyspeck disease caused by S. emperorae on apple fruits, alongside the identification of a new host for S. wisconsinense in Korea.