Ecofriendly synthesis and characterization of copper chitosan nanoparticles (CuChNPs) and assessing combined effect of nanoparticles and bismerthiozol against bacterial leaf blight of rice

The rice bacterial blight pathogen, Xanthomonas oryzae pv. oryzae (Xoo), poses a major threat to global rice production. While chitosan and copper-based nanoparticles have been explored for plant disease control, their potential to function as synergistic boosters for reducing conventional agrochemical dosage remains largely underexploited. Keeping this in mind and risks associated with traditional chemical treatments, this study focused on the eco-friendly synthesis of crystalline copper-chitosan nanoparticles (CuChNPs) designed to function as a sustainable synergistic booster enhancing antibacterial efficacy against Xoo. To evaluate the effectiveness of CuChNPs alone and in combination with Bismerthiozol (0.15%, 0.125%, and 0.1%) at CuChNPs: dH₂O ratios of 6:4 and 4:6 under net-house conditions, ten treatments were compared against controls (Bismerthiozol 0.2% and CuChNPs 10:0). All treatments were applied as foliar sprays before and after inoculation, with the 6:4 and 4:6 ratios selected due to their lower dosage requirement and superior in vitro performance. The successful synthesized of crystalline shaped nanoparticles were confirmed by UV-visible spectroscopy. SEM and TEM analyses revealed a distinct morphology with an average particle size of 110.23 nm and zeta potential of -23.1 mV indicating strong colloidal stability. In vitro assays showed strong antibacterial activity of CuChNPs against Xoo, while CuChNPs with bismerthiozol (0.15%) demonstrated notable disease reduction (63.78% at 14 days and 58.09% at 21 days) in net-house conditions. Field trials confirmed this superior performance, with the same treatment achieving 54% and 57.88% disease reduction at 14 and 21 days, respectively. Overall, these findings conclude that CuChNPs serves as an effective, stable and eco-friendly alternative for managing rice bacterial blight, while promoting sustainable rice production and global food security through reduced hazardous agro-chemical usage.