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

Abstract 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.