Zinc oxide nanoparticles enable sustainable disease management in tea by dual nutrient and antifungal action

Zinc oxide nanoparticles (ZnO-NPs) are emerging as effective micronutrient carriers with additional antifungal properties. However, their application in perennial plantation crops such as tea (Camellia sinensis) remains unexplored. Fusarium solani, a destructive soil-borne pathogen, poses a significant challenge in tea nurseries and plantations. Greenhouse pot trials were conducted using ZnO-NPs at 3, 6, and 9 mg kg^-1, with ZnSO₄·7H₂O serving as the conventional zinc control. Disease severity, rhizosphere colony-forming units (CFU) populations, soil zinc availability, foliar uptake, microbial biomass, and chlorophyll traits were assessed over 30 days. ZnO-NPs reduced disease severity by 18-55 % and suppressed rhizosphere F. solani CFU counts by up to 69 %, significantly outperforming ZnSO₄·7H₂O. They increased DTPA-extractable soil Zn (to 0.84 mg kg^-1) and improved foliar Zn uptake. In comparison, the 6 mg kg^-1 dose enhanced chlorophyll a and total chlorophyll, while maintaining near-baseline microbial biomass. Although the 9 mg kg^-1 dose yielded higher pathogen suppression, it reduced microbial biomass carbon by 19 %. Microscopy confirmed collapsed hyphae and deformed conidia, consistent with oxidative stress and cell wall disruption. This study provides the first greenhouse-based evidence that ZnO-NPs can function as dual-action soil amendments in tea, improving both nutrient status and resistance to F. solani. The intermediate rate (6 mg kg^-1) delivered the best balance between plant benefits and microbial stability, highlighting the agronomic promise of nano-enabled inputs. Further multi-season field studies are needed to verify their effectiveness and environmental safety.