Three Colletotrichum species associated with anthracnose of tropical fruit crops in Southern Karnataka and Andhra Pradesh, India

Abstract

Severe pre and post-harvest losses occur in tropical fruit crops by fruit rot pathogens especially Colletotrichum spp., causing anthracnose disease. The wide host range of the pathogen is associated with the prevalence of different species in the fruit orchards. Hence, the diversity of Colletotrichum spp. was explored for sustainable disease management and plant biosecurity. Anthracnose samples were collected from orchards of cultivated tropical fruit crops in Southern Karnataka and Andhra Pradesh, India. Characteristic symptoms of anthracnose included dark, sunken lesions with visible acervular aggregates at advanced stages of infection. Preliminary identification of nine isolates (IIHR_COL_C1-9) was based on morpho-cultural characteristics. Eight isolates were assigned to the C. gloeosporioides species complex, producing cylindrical conidia and white aerial mycelial colonies, while one isolate (IIHR_COL_C8) was identified as C. truncatum, producing falcate conidia and dark grey colonies with concentric zonation. Multigene phylogenetic analysis using partial sequences of ITS, ACT, GD, SOD2 and TUB2 in MEGA X further resolved the isolates into three species: C. siamense (n=7), C. musae (n=1), and C. truncatum (n=1). The mean conidial size of C. siamense ranged from 10.16 – 14.18 µm × 3.76–5.34 µm, C. musae is 12.01 × 3.83 µm, and C. truncatum is 21.45 µm × 2.57 µm. The mean growth rate of C. siamense ranged from 10.56 – 12.92 mm/day, C. musae was 12.61 mm/day, and C. truncatum was 7.47 mm/day. C. siamense was identified as the dominant species causing anthracnose disease across all seven fruit crops viz., Banana, Custard Apple, Guava, Grape, Mango, Papaya and Pomegranate, along with C. musae identified from Banana and C. truncatum from Papaya.