Antifungal mechanisms and characterization of gold nanoparticles: a strategic approach to combat Colletotrichum capsici-induced anthracnose disease and enhance chilli growth

Abstract Gold nanoparticles (Au-NPs) show antagonistic potential against a wide range of pathogenic fungi. In this study, we report the antifungal potential of Au-NPs in suppressing anthracnose disease on chilli plants. The results demonstrate that 90 mg/L of Au-NPs effectively inhibited the mycelial growth of Colletotrichum capsici , enhanced relative membrane permeability and reduced disease incidence in chilli pepper plants. These results were confirmed using confocal microscopy, in which Au-NPs eliminate the C. capsici hyphae from the pericarp cells of chilli fruits. Additionally, Au-NP treatments led to a marked increase in total phenol, chlorophyll, free amino acid, and glycine betaine compared to untreated control and C. capsici -infected plants. Moreover, both individual and combined treatments with Au-NPs statistically enhanced the concentrations of phosphorus, nitrogen, zinc, and potassium in the roots, leaves, and fruits. Au-NPs also improved the plant's resilience to stress by activating the expression of defense-related genes and transcription factors during C. capsici infection. These findings reveal that Au-NPs can serve as antifungal agents against anthracnose disease, while simultaneously enhancing plant immunity and growth.