Selenium nanoparticle-mediated rice defense against bacterial brown leaf spot caused by Pseudomonas syringae pv. syringae

Abstract Rice bacterial brown leaf spot is a destructive disease caused by the pathogen Pseudomonas syringae pv . syringae . This research evaluated the role of selenium nanoparticles (SeNPs) in plant defense against rice bacterial brown leaf spot disease and compared the effect of SeNPs with sodium selenate. We used 5 different concentrations (10, 20, 30, 40, and 50 mg/L) of both SeNPs and sodium selenate to determine the most effective dosage for maximizing their benefits while minimizing the risk of selenium toxicity. Results showed that plants treated with 30 mg/L SeNPs performed the best, exhibiting the highest relative control effect of 64.16%, followed by plants treated with 30 mg/L of sodium selenate, which showed a relative control effect of 60.67%. Both SeNPs and sodium selenate significantly influenced rice defense mechanisms, but SeNPs performed better in all aspects, resulting in lower disease incidence compared to sodium selenate. SeNPs significantly increased the chlorophyll content, boosted levels of total soluble phenolics (TSP), lignin-thioglycolic acid (LTGA), and defense-related enzymes such as phenylalanine ammonia-lyase (PAL), peroxidase (POD), superoxide dismutase (SOD), polyphenol-oxidase (PPO), catalase (CAT), and β-1,3-glucanase. Furthermore, SeNPs significantly decreased the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), and enhanced the expression of plant defense-related genes such as OsPr1b, PAL, CatA , and POX . These findings suggest that SeNPs enhance the defense responses of rice against bacterial brown leaf spot and could serve as an effective and sustainable tool for crop protection.