Green-synthesized ZnO nanoparticles from Capparis aphylla enhance rice growth and defense responses against Rhizoctonia solani.

INTRODUCTION: Fungal diseases pose a major threat to global agriculture, reducing crop yield and quality while contributing to environmental and health concerns through excessive use of chemical fungicides. Green nanotechnology utilizing plant extracts has emerged as a promising approach for managing plant diseases. We provide, for the first time, a green nano-fungicide that demonstrates dual action: direct antifungal efficacy against Rhizoctonia solani, enhancement of plant development, and upregulation of rice defense enzymes. METHODS: In this study, zinc oxide nanoparticles (ZnONPs) were synthesized using leaf extract of the indigenous medicinal plant Capparis aphyla and characterized for their physicochemical and biological properties. FTIR analysis confirmed the presence of functional biomolecules such as alcohols, thiols, isothiocyanates, and aromatics acting as stabilizing and reducing agents. XRD revealed the crystalline nature of ZnONPs with an average particle size of 21 nm, while EDX and SEM confirmed their elemental composition and morphology. RESULT AND DISCUSSION: The green-synthesized ZnONPs exhibited strong antifungal activity against major phytopathogens, showing the highest inhibition against Rhizoctonia solani (85.2%), followed by Fusarium oxysporum (75.0%) and Alternaria alternata (71.6%) at 1000 µg/mL. SEM and TEM analyses demonstrated severe morphological alterations and membrane disruption in R. solani hyphae, suggesting oxidative stress as a key mechanism of action. In greenhouse trials, ZnONP treatment significantly improved rice growth parameters, including biomass, root and shoot length, and dry weight, in a concentration-dependent manner. Furthermore, enhanced activities of SOD, POD, CAT, and proline, along with reduced MDA levels and disease index, indicated improved oxidative defense. RT-qPCR analysis further confirmed upregulation of defense-related genes (SOD, PR1, PR1a, and PPO). These results demonstrate that C. aphyla-mediated ZnONPs offer an eco-friendly, cost-effective, and potent strategy for sustainable crop protection.