Beyond silver: innovative use of gold nanoparticles for anthracnose management and plant immunity enhancement in chilli

BACKGROUND: Silver nanoparticles (Ag-NPs) have been explored for their antifungal properties in previous studies, yet gold nanoparticles (Au-NPs) offer distinct advantages owing to their biocompatibility, stability and multifunctional roles in plants. RESULTS: Au-NPs inhibited Colletotrichum gloeosporioides mycelial growth by 61% and reduced spore germination to 25%, while increasing membrane permeability and lowering disease incidence to 21% in detached fruits and 17% in attached fruits. Beyond pathogen suppression, Au-NPs uniquely enhanced plant physiology, significantly increasing total phenols, chlorophyll, free amino acids and glycine betaine. Unlike Ag-NPs, Au-NPs improved nutrient uptake and translocation, elevating phosphorus, nitrogen, zinc and potassium concentrations in roots, leaves and fruits, likely via modulation of root physiology. Moreover, Au-NPs activated defense-related genes and transcription factors, boosting plant resilience during infection. CONCLUSION: This study highlights the innovative dual functionality of Au-NPs, combining potent antifungal action with plant growth and immunity enhancement, positioning them as a superior and sustainable alternative to traditional silver-based nanoparticle approaches in crop protection. © 2026 Society of Chemical Industry.