Cultural, morphological and pathological variability in Colletotrichum gloeosporioides isolates from onion anthracnose in Maharashtra’s Marathwada region

Maharashtra is the leading producer of onions, which are grown in three seasons: kharif, rabi, and summer. . Anthracnose (Colletotrichum gloeosporioides) is one of the most significant constraints in onion cultivation. The pathogen is polyphagous, infecting crops such as onion, garlic, shallot and other Allium crops. Anthracnose diseased onion crop specimens were collected from various locations, and the test pathogen was isolated on potato dextrose agar (PDA). C. gloeosporioides isolates (Cg-1, Cg-2, Cg-3, and Cg-4) were purified and grown on PDA slant. C. gloeosporioides isolates showed a wide range of cultural, morphological, and pathogenic variability. The colony diameter/growth of the test isolates ranged from 50.02 to 80.00 mm. However, it was highest with the isolate Cg-1 (80.00 mm), followed by Cg-2 (68.18 mm), Cg-4 (60.56 mm), and Cg-3 (60.56 mm) (50.02 mm). Morphological characteristics of C. gloeosporioides test isolates revealed variability in conidial size, with Cg1 isolate having the largest conidia (21.45x8.63m), followed by Cg4 (19.65x8.08 m) and Cg2 (19.45x6.82 m). Pathogenic variability revealed a wide range of pathogenicity among the test isolates, including highly virulent (Cg1) and moderately virulent (Cg2) isolates (Cg2, Cg3, Cg4).