Modulation of Antioxidant System Under Drought Conditions in Red Kidney Bean by Chitosan

The study examines the impact of climate change-induced drought on red kidney bean (Phaseolus vulgaris L.) cv. VL Rajma 63 and evaluates the effectiveness of 0.25% of seed chitosan application priming and foliage spray under restricted irrigation. Specifically, it assesses how chitosan treatment enhances the antioxidant potential in response to varying degrees of drought stress. The protein content of all treated leaves ranged between 12.00 and 41.55 mg/g fresh weight in primed plants. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) of leaf proteins expounded new polypeptides in the range of 69.8 to 9.9 kDa. The unprimed plants under severe drought stress showed 3.86 folds of higher hydrogen peroxide compared to control on the 70th day after sowing (DAS). The seed primed plant showed the highest superoxide dismutase (SOD) activity of 2.57 ± 0.01 U/mg protein on the 70th DAS with 20% irrigation in VL Rajma 63 (SPV20). The highest polyphenol oxidase (PPO) activity was observed with the treatment SPV20 (2.22 ± 0.01 ∆O.D./min/mg protein) on the 70th DAS. Hydrogen peroxide showed a strong positive correlation between antioxidant enzymes. Native PAGE (12%) assays revealed four, six, and four isoforms of SOD, guaiacol peroxidase (GPOX), and PPO. The isoenzymes Mn-SOD (Rf 0.14), Fe-SOD (Rf 0.24), CuZn-SOD I (Rf 0.36), CuZn-SOD II (Rf 0.46), GPOX 1–4, and PPO 1–4 were upregulated with varying degrees of drought stress. This study significantly extends the role of seed biopriming as a better option than foliage spray for augmenting drought tolerance.