Enzymatic activity assays and functional component profiling reveals coordinated defense response of mungbean against Cercospora canescens during leaf spot disease

Cercospora leaf spot (CLS) caused by Cercospora canescens is a formidable seed-borne disease and survives in crop debris or other host plants affecting mungbean cultivation. This study presents a comparative assessment of enzymatic activity assays and functional components in mungbean, focusing on the relationship of host plant and the pathogen, responsible for CLS. Comparative analyses were conducted between susceptible and resistant genotypes in both inoculated and uninoculated conditions to analyze defense-related activity like ascorbate peroxidase (APX), peroxidase (POD), lipid peroxidase (LPX), and catalase (CAT). In addition, C-based compounds including total phenols and flavonoids were analyzed through detached mungbean leaf method. The study further extended its analysis beyond leaves to other parts like pods, stems, and seeds. The host–pathogen relationship was investigated at various stages; control, 2 days after inoculation (DAI), 4 DAI, 6 DAI. At 6 DAI (T4), in the pods, the enzyme activity was 3.1-fold higher for ascorbate peroxidase, two-fold higher for peroxidase, and 1.8-fold higher for lipid peroxidase in case of susceptible genotype in contrast to mock inoculation (T1). For resistant genotype, the antioxidant activity at 6 DAI (T4) was 3.7-fold higher for ascorbate peroxidase, 2.73-fold higher for peroxidase, 1.8-fold higher for lipid peroxidase, and 2.7-fold higher for catalase compared to mock inoculation (T1). In pods, catalase activity was upregulated by 1.47-fold in resistant genotype and conversely, its activity was downregulated by 1.30-fold in pods of susceptible genotype at 6 DAI. Results indicate a positive regulation of catalase in pods of resistant genotype throughout infection period. These findings underscore the plant’s ability to mount a well-coordinated defense response, involving multiple components of the anti-oxidative system. The sophisticated regulation of these defense mechanisms reflects the adaptability and resilience of mungbean plants against pathogen challenges.