Integrated Physiological and Biochemical Responses of Mungbean (Vigna radiata) to Alternaria alternata

Alternaria alternata causes severe foliar disease and substantial yield losses in mung bean (Vigna radiata (L.) R. Wilczek). However, the physiological and hormonal mechanisms driving resistance in locally adapted varieties remain largely unknown. We evaluated nine genotypes of Uzbekistan under controlled A. alternata inoculation across four growth stages (budding, flowering, podding, harvest), measuring salicylic acid (SA), jasmonic acid (JA), photosynthetic pigments, leaf water relations, morphology, and yield components. Infection triggered highly variable SA responses. Surprisingly, strong SA induction offered no yield protection: Barqaror showed a 212% SA increase but suffered the most severe grain weight loss (−62.6%). Conversely, Turon maintained high baseline JA and was the only genotype to increase chlorophyll a at podding (+16.8%). Disease stress did not significantly affect 1000-seed weight (p = 0.184), indicating that A. alternata primarily disrupts early pod formation rather than the seed-filling process. Zilola demonstrated the best overall yield stability, exhibiting near-complete pod retention (−0.8%) and moderate grain weight loss (−26.7%) while maintaining acceptable seed size. These findings emphasize that protecting early pod set is more critical than seed-filling capacity under infection. Consequently, Zilola represents a highly promising parental line for breeding A. alternata-tolerant mung beans in Central Asia.