Identification and Characterization of Diplodia parva and Diplodia crataegicola Causing Black Rot of Chinese Quince

Fungal isolates from infected Chinese quince trees were found to cause black rot in Yeongcheon, Gyeong-sangbuk Province, Korea. The quince leaves withered and turned reddish-brown and fruits underwent black mummification. To elucidate the cause of these symp-toms, the pathogen was isolated from infected leaf and fruit tissues on potato dextrose agar and Levan media. Several fungal colonies forming a fluffy white or dark gray mycelium and two types of fungi forming an aerial white mycelium, growing widely at the edges, were iso-lated. Microscopic observations, investigation of fungal growth characteristics on various media, and molecu-lar identification using an internal transcribed spacer, β-tubulin, and translation elongation factor 1-α genes were performed. The fungal pathogens were identified as Diplodia parva and Diplodia crataegicola. Pathogenic-ity tests revealed that the pathogen-inoculated fruits ex-hibited a layered pattern, turning brown rotting; leaves showed circular brown necrotic lesions. The developed symptoms were similar to those observed in the field. Fungal pathogens were reisolated to fulfill Koch’s pos-tulates. Apples were inoculated with fungal pathogens to investigate the host range. Strong pathogenicity was evident in the fruits, with browning and rotting symp-toms 3 days after inoculation. To determine pathogen control, a fungicidal sensitivity test was conducted us-ing four registered fungicides. Thiophanate-methyl, propineb, and tebuconazole inhibited the mycelial growth of pathogens. To the best of our knowledge, this is the first report on the isolation and identification of the fungal pathogens D. parva and D. crataegicola from infected fruits and leaves of Chinese quince, causing black rot disease in Korea.