ASSESSMENT AND CHARACTERIZATION OF COLLETOTRICHUM SPECIES CAUSING BITTER ROT DISEASE OF APPLE IN QUETTA

Colletotrichum species pose a significant threat to the economy of Pakistan, primarily due to the favorable environmental conditions that facilitate pathogen dispersal. This research was conducted to accurately identify Colletotrichum species and study their pathogenic behavior, which is responsible for pre-harvest bitter rot disease in apple fruits in Quetta, Pakistan. A survey was conducted across ten locations in Quetta to assess disease prevalence and collect samples. The findings revealed a disease incidence of 39.22% in one season and 32.56% in another. The symptoms included sunken brown lesions, measuring 1-4 cm in diameter, on the fruit surface, containing small, pinhead-sized black fruiting structures. A total of 130 fungal isolates were obtained from infected samples and were primarily categorized into three groups (A, B, C) based on distinct cultural and morphological characteristics. Pathogenicity test confirmed Colletotrichum as the causative pathogen. Further, ten isolates from each group were subjected to molecular analysis to identify the Colletotrichum species using internal transcribed spacer (ITS), beta-tubulin (TUB), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene regions. Sequence analysis identified the fungal isolates as three Colletotrichum species: Group (A) C. acutatum, Group (B) C. gloeosporioides, and Group (C) C. siamense. To our knowledge, this is the first comprehensive study of Colletotrichum spp. causing bitter rot disease of apples in Pakistan. The findings of our research will pave the way for future disease management strategies, aiming to prevent this disease from becoming a more serious threat in the region.