Comprehensive analysis of blackgram resistance to powdery mildew: Morphological, physiological and biochemical perspectives

Powdery mildew poses a significant threat to blackgram (Vigna mungo L.) productivity, demanding sustainable solutions rooted in host resistance. In this study, 121 blackgram genotypes were initially field-screened to capture the spectrum of disease response. From this pool, seventeen genotypes ranging from moderately resistant to highly susceptible were subjected to detailed morphological and physiological assessments. Among them, eight representative genotypes (four moderately resistant and four highly susceptible) were further analyzed for key biochemical and enzymatic responses, revealing distinct defense-associated profiles. Moderately resistant lines demonstrated superior surface wax deposition (TBG-138: 140.33 mg dm⁻²; LBG-648: 108.00 mg dm⁻²), higher trichome density (LBG-648: 27.33 per 5 mm²) and lower stomatal frequency (PBG-23: 76.53 mm⁻²; TBG-138: 102.04 mm⁻²) traits, likely restricting pathogen entry. Biochemically, resistant genotypes exhibited elevated phenol levels, while susceptible ones accumulated more sugars, potentially favoring fungal colonization. Enzymatic assays highlighted intensified activity of key defense enzymes like peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) in resistant lines, pointing to a stronger immune response. Multivariate analysis reinforced these associations like surface wax and enzymatic defense were negatively correlated with disease severity, while stomatal frequency and sugar content showed positive correlations. Collectively, this integrative study identifies pivotal traits conferring resistance and lays a foundation for breeding resilient blackgram varieties, aligning with the principles of sustainable and eco-conscious agriculture.