Phenotypic Evaluation and Defense-Related Biochemical Activities in Peduncles of Basmati Rice Against Neck Blast Fungus, Magnaporthe oryzae

This study investigates the phenotypic responses and defense-related enzymes in the infected peduncles of basmati rice against neck blast fungus, Magnaporthe oryzae, across eight basmati rice genotypes in Punjab. The genotypes INGR 15001, INGR 15002, Pusa Basmati 1637, Pusa Basmati 1884, Pusa Basmati 1401, Pusa Basmati 1121, Punjab Basmati 7, and Tetep exhibited varying degrees of resistance. Genotypes INGR 15001, INGR 15002, Pusa Basmati 1637, Tetep, and Pusa Basmati 1884 showed moderate resistance, with Susceptibility Index (Sx) values below 3.0, AUDPC values between 90.0 and 99.3, and lesion length ranging from 5.00 to 6.70 mm. While, Pusa Basmati 1121 and Punjab Basmati 7 were adjudged as susceptible (6.0<Sx<9.0) to neck blast disease. Genotype Pusa Basmati 1401 displayed highly susceptible response, with Sx value of 9.00. Enzyme activity assays of peduncles conducted at 0, 3 and 9 days post-inoculation, revealed that moderately resistant genotypes had significantly higher activities of peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, catalase, and hydrogen peroxide compared to the susceptible genotypes. The findings in this study reveal a significant negative correlation between lesion length and the activities of key defense-related enzymes (POX, H₂O₂, PAL, PPO, and CAT) in infected peduncles, suggesting their role in restricting neck blast severity. Further, a strong positive correlation among these enzymes and H₂O₂ content highlights their synergistic involvement in the biochemical defense mechanism against M. oryzae. The findings explore the potential of defense-related enzymes in contributing resistance to neck blast phase in basmati rice genotypes.