Bioengineered nano zinc oxide formulation-SmZnF disrupting fungal pathogens of Withania somnifera, a high value medicinal plant

Fungal phytopathogens pose significant challenges to agriculture owing to their high genetic diversity, adaptability to environmental conditions, and rapid evolutionary dynamics, which enable them to develop resistance against commonly used chemical fungicides and even overcome disease-resistant plant varieties. Zinc oxide nanoparticles (ZnO-NP) have emerged as potent antifungal agents due to their safety and unique physicochemical properties. In the present study, fungal diseases affecting Withania somnifera were effectively managed using a nano-bioformulation (SmZnF). We carried out a comprehensive physicochemical analysis and confirmed the stability and efficacy of SmZnF. The in vitro fungicidal activity illustrated that the MIC of SmZnF on Fusarium solani , WsRrK-01, 125 µg/ml, Alternaria alternata , WLSK-01, 62.5 µg/ml, and Sclerotinia sclerotiorum , WsSRK-01, 15.625 µg/ml was significantly more effective than the ZnO-NP alone. The mode of action of SmZnF on phytopathogenic fungi revealed that the electrolyte and sugar leakage from the mycelia, and alteration in total mycelial ergosterol content, lead to disruption and rupture of the mycelia. The morphological distortion and biochemical findings confirmed the mode of action of SmZnF, and the bio-efficacy of SmZnF was validated through in planta antifungal assays under glasshouse. • The SmZnF effectively controlled the major fungal pathogens of Withania somnifera . • The SmZnF exhibited enhanced synergistic fungicidal activity in terms of MIC on Fusarium solani (125 µg/ml), Alternaria alternata (62.5 µg/ml), and Sclerotinia sclerotiorum (15.625 µg/ml). • The mode of antifungal activity of SmZnF includes leakage of electrolyte and sugar, and alteration of ergosterol content in the mycelia, leads to disruption, rupture and death of the fungal cell. • The bio-efficacy of SmZnF confirmed the effective management of fungal diseases under the controlled glasshouse environment.