Green mycosynthesis of ZnO nanoparticles enhances antifungal defense against Fusarium equiseti through metabolic and gene expression modulation

The soil borne phytopathogen Fusarium equiseti poses a significant threat to global crop production, with limited sustainable control options. In this study, zinc oxide nanoparticles (ZnO-NPs) were green-synthesized using the extracellular filtrate of Trichoderma asperellum and characterized by SEM, XRD, FTIR, DLS, and Zeta potential apparatuses. The biosynthesized ZnO-NPs exhibited a quasi-spherical morphology with a size range of 13-19 nm, high crystallinity, and a stable negative zeta potential (- 27 mV). FTIR confirmed successful ZnO-NPs formation through the characteristic absorption band at 599 cm^-1. Antifungal assays revealed a concentration dependent inhibition of mycelial growth in two examined strains of F. equiseti, achieving maximum suppression of 72.41 ± 0.01 and 73.41 ± 1.16% at 5 mg mL^-1, comparable to the commercial fungicide Propiconazole (5 mg mL^-1) with inhibition rates reaching 82.75 ± 0.75% for F. equiseti st.1 and 85.49 ± 0.68% for F. equiseti st.2. GC-MS profiling of the treated fungal filtrates indicated that, ZnO-NPs induced distinct metabolic alterations, including the appearance of stress associated metabolites such as phomenone, alongside modulation of membrane active glycol ethers when compared with the non-treated fungi. qRT-PCR analysis showed that ZnO-NPs selectively enhanced the expression of defense related genes (PR2, PPO, PR5, and PR8) in two strain of F. equiseti, while response efficacy was differed between the two strains. These findings demonstrate that mycosynthesized ZnO-NPs exert potent antifungal activity through combined physical disruption and biochemical interference, offering a promising eco-friendly alternative to synthetic fungicides for sustainable crop protection.