Field reaction and metabolic alterations in grape (Vitis vinifera L.) varieties infested with anthracnose

The present study was conducted to evaluate the biochemical response of five selected grape varieties (H 516, Pusa Navrang, Flame Seedless, Beauty Seedless and Perlette) to anthracnose incidence under field conditions. The selected grape varieties were screened for their reaction during the peak disease incidence according to a standard disease scoring technique (0-5) to estimate percent disease index (PDI). Results showed that H 516 was resistant (PDI = 0.66), Pusa Navrang (PDI = 27.66) and Flame Seedless (PDI = 36.33) rated as moderately resistant varieties, whereas varieties Beauty Seedless (PDI = 61.66) and Perlette (PDI = 73.00) are rated as susceptible to the disease. The level of different biochemical constituents were examined in healthy and anthracnose infected leaves for their possible association with disease resistance. The infected leaves of resistant variety (H 516) showed higher levels of total soluble sugars (8.04 mg/g DW), total soluble proteins (1.05 mg/g DW), free amino acids (0.107 mg/g DW), total phenols (5.64 mg/g DW), proline (52.01 μg/g FW), α-tocopherol (2.39 mg/g DW, peroxidase activity (3.51 ΔA/min/g FW) and polyphenol oxidase activity (0.0224 ΔA/min/g FW) from their healthy counterparts and these were significantly different from the other evaluated varieties. MDA content was significantly higher in the most susceptible variety Perlette. A decrease in the content of chlorophyll, carotenoids and ascorbic acid was recorded in infected leaves as compared to their healthy counterparts. Highest Pearson correlation coefficient was reported between PDI and chlorophyll b (r = −0.886**) followed by phenols (r = −0.846**).