Fabrication, Characterization, and Antifungal Activity of Chitosan-Cyproconazole Nanocomposite for Simultaneous Wheat Stem Rust Control and Growth Enhancement.

The stem rust disease caused by obligate biotrophic fungus Puccinia graminis f. sp. tritici is a worldwide threat to the global wheat production with frequent epidemics leading to widespread reliance on chemical fungicides such as cyproconazole. To reduce fungicide risks on human health and environmental integrity, chitosan nanoparticles (CNPs) and novel chitosan-cyproconazole nanocomposite (Chi-Cyp) were synthesized. Dynamic light scattering (DLS) and Fourier transform infrared (FTIR) spectroscopy confirmed the size of 80-90 nm and surface charge and uniformity. To evaluate their efficacy against the disease, various concentrations of CNP and Chi-Cyp were applied via irrigation, foliar spray, and a combination of both methods. Wheat seedlings were treated 24 h prior to inoculation, as well as at 48- and 96-h post-inoculation with Pgt urediniospores. Phenotypic assessments conducted 2 weeks post-inoculation revealed that CNPs (100 μg/mL) and Chi-Cyp (1 μg/mL), along with the positive control cyproconazole (10 μg/mL), significantly suppressed stem rust infection. Quantitative polymerase chain reaction (qPCR) analysis corroborated these findings, demonstrating a substantial reduction in fungal biomass in treated plants. Additionally, the impact of the nanomaterials on plant growth parameters was examined. Notably, Chi-Cyp treatment at 50 μg/mL significantly enhanced seedling growth, as evidenced by increased shoot and root lengths, and elevated fresh and dry biomass accumulation. This study highlights the potential of the Chi-Cyp nanocomposite, which contains a 10-fold lower concentration of cyproconazole, to effectively control stem rust with comparable efficacy to the fungicide alone. These findings underscore the promise of nanotechnology-based strategies in sustainable plant disease management.