Zinc-chitosan nanocomposites as guardians against the dreaded phytopathogenic fungus Macrophomina phaseolina in Vigna radiata L.

• Chitosan-mediated zinc nanoparticles (Zn-ChNPs) prepared by via the ionic gelation method were well-characterized by UV, XRD, and FTIR analysis. • In vitro bioassays revealed that increasing concentrations of Zn-ChNPs drastically affected fungal growth, distorted fungal hyphae and altered enzymatic activity. • In planta bioassays also ensured effective management of the charcoal rot disease in mung bean plant and improved plant growth and biochemical attributes. • Zn-ChNPs proven antifungal potential to be used as an alternative to synthetic fungicide. Macrophomina phaseolina, a phytopathogenic fungus responsible for root rot in mung beans ( Vigna radiata L.), produces resilient sclerotia that are not effectively managed by chemical fungicides. In this study, as an alternative management approach, zinc-chitosan nanoparticles (Zn-ChNPs) were prepared using the ionic gelation method and evaluated for their antifungal activity against M. phaseolina. The synthesis of Zn-ChNPs was confirmed by UV–visible spectroscopy with absorption peaks at 215 nm and 265 nm. XRD indicated hexagonal crystalline planes, verifying nanoparticle crystallinity, while FTIR showed strong ZnO-chitosan interactions with peaks at 3495 cm⁻¹ and 678 cm⁻¹. The particles averaged 80–100 nm in size . Antifungal bioassays demonstrated significant inhibition of fungal growth, achieving 50–100 % reduction at concentrations of 0.11 % and above, and an EC 50 (effective concentration) value of 0.08 %. Microscopic analysis revealed sclerotia distortion at 0.15 % Zn-ChNPs, while enzymatic assays showed a 20–60 % increase in catalase, peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase activities at concentrations of 0.03–0.11 %, followed by a sharp decrease beyond 0.11 %. In planta bioassays indicated that 0.4–0.6 % Zn-ChNPs reduced disease by 97 % and improved growth up to 100 %, surpassing the performance of chemical fungicides (Carbendazim). Multivariate analysis further underscored the superior efficacy of Zn-ChNPs in enhancing plant defense mechanisms and managing root rot disease. These findings highlighted the potential of Zn-ChNPs as a sustainable and effective alternative to chemical fungicides, offering dual benefits of disease control and growth enhancement in mung bean plants.