Unveiling Biochemical Dynamics in Common Bean-Pseudocercospora Pathosystem Under Angular Leaf Spot Pressure in Western Himalayan Kashmir

Angular leaf spot (ALS) is one of the most catastrophic diseases limiting the production of common bean. The present study was the first comprehensive study to characterize the biochemical basis of differential response of common bean resistance/susceptibility to angular leaf spot pathogen. Two hundred germplasm accessions were evaluated under field conditions in the year 2022 and 2023. Pooled over years, under the field conditions, 20 genotypes (10%) were completely resistant, 14 (7%) moderately resistant, 64 (32%) moderately susceptible and 102 were completely susceptible (51%). Sixty contrasting genotypes were selected for the artificial inoculation (using isolate Pg 02) in the greenhouse and the mean disease score of resistant and susceptible genotypes was 1.06 and 7.18 respectively. All biochemical parameters, except phenols and alkaloids, were significantly higher (p < 0.05) in resistant genotypes as compared to susceptible ones. The fold increase was highest in case of chlorophyll (2.91) followed by tannins (1.58), total sugars (1.31) and catalase (1.02), whereas, lower fold increases were recorded in case of MDA (0.21), ascorbic acid (0.24), glycine betaine (0.50) and proline (0.59). The results of this study established that there is definite biochemical basis of differential response of common bean genotypes against ALS pathogen and substantiated the hypothesis that defense-related enzymatic and non-enzymatic antioxidative biochemicals are activated to counter the reactive oxygen species (ROS) driven damage and induce systemic resistance upon invasion by ALS pathogen.