Exploring silver nanoparticles for chilli disease management: Synthesis, characterization and antimicrobial insights

This research demonstrates the eco-friendly synthesis of silver nanoparticles with Azadirachta indica A. Juss. leaf extract and assesses their antibacterial efficacy, particularly against Fusarium solani a major plant pathogen affecting chilli peppers. F. solani was isolated from infected chilli plant material and identified using morphological and molecular markers. The EF-1α and β-tubulin genes were employed for precise molecular identification. Driven by increasing concerns about the environmental and health risks associated with chemical fungicides, this study explores a sustainable and eco-friendly alternative. The produced AgNPs were fully characterized utilizing a range of techniques, beside UV–vis, ζ-potential, DLS, TEM, FTIR and XRD. The nanoparticles displayed a stable, spherical particles, measuring 10–40 nm. The in vitro antimicrobial efficacy against Fusarium solani , Escherichia coli and Staphylococcus aureus was assessed. A concentration-dependent antibacterial effect was observed, with inhibition zones of 18.67 ± 0.47 mm against E. coli and 16.33 ± 0.47 mm against S. aureus at a silver nanoparticle concentration of 100 μg/mL. Superior antifungal activity against Fusarium solani was demonstrated by AgNPs at 50 μg/mL, exceeding that of the standard fungicide carbendazim. Structural damage to the fungal hyphae was further verified through SEM imaging, supporting the involvement of cell wall breakdown as major modes of action. Overall, the findings emphasize the effectiveness of neem-derived AgNPs as a viable, environmentally friendly alternative to synthetic antimicrobial agents, with promising applications in agricultural disease management and beyond.