Progression of Anthracnose Disease in Grape Varieties

Abstract

Grape (Vitis vinifera L.) constitutes a fruit crop of considerable economic significance; however, its productivity is markedly limited by several fungal pathogens, notably downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator), anthracnose (Colletotrichum gloeosporioides), and Botrytis bunch rot (Botrytis cinerea). Among these diseases, anthracnose incited by C. gloeosporioides is particularly destructive, frequently resulting in substantial yield losses, deterioration of fruit quality, and reduced market value when environmental conditions favour disease development. The intensity of anthracnose was evaluated in eight grape cultivars during the back-pruning seasons of 2024 and 2025 at Raichur. Among the cultivars tested, Thompson Seedless demonstrated the earliest manifestation of disease symptoms and the most rapid disease advancement, reaching a per cent disease index (PDI) of 100 in both seasons. This cultivar also recorded the highest values for the area under the disease progress curve (AUDPC) and the apparent infection rate. Fantacy Seedless and Medica showed comparatively slower disease progression, while Sharad Seedless, K. R. White and Manjari Naveen exhibited moderate disease development. however, all varieties were classified as highly susceptible. Weekly monitoring of anthracnose in Thompson Seedless during Kharif 2024 and 2025 showed disease appearance in the 27thSMW (8.50 PDI) in 2024 and in the 24thSMW (7.13 PDI) in 2025, reaching 100 PDI by the 39thand 35thSMW, respectively. The highest apparent infection rate was recorded at the 36thSMW (r = 0.105) in 2024 and at the 29thSMW (r = 0.119) in 2025, with cumulative AUDPC values of 4319.00 and 4110.30, respectively, highlighting rapid disease buildup and the need for timely disease management during back pruning.