Abstract
BACKGROUND: Rice blast, caused by Pyricularia oryzae, poses a formidable threat to global rice production. Given that chemical fungicides, one of the important methods used to control rice blast, cause harm to the environment and human health, sustainable alternatives are required. This study aimed to synthesize silver nanoparticles (AgNPs) with antifungal activities against P. oryzae using mangrove soil bacteria, and to evaluate their ecotoxicity. RESULTS: In this study, AgNPs were synthesized using fermentation extracts from Pseudomonas aeruginosa R64. The resulting nanoparticles (RFE-AgNPs), ranging in size from 4.516 to 37.031 nm, were characterized by UV-visible spectroscopy and high-resolution transmission electron microscopy equipped with energy dispersive spectroscopy. RFE-AgNPs at 20 μg mL(-1) had strong antifungal activity against P. oryzae, inhibiting colony growth by 77%. Moreover, RFE-AgNPs significantly hindered conidial germination, germ tube elongation and appressorium formation. In addition, microscopic observation revealed that RFE-AgNPs treatment disrupted mycelial morphology, lipid and glycogen metabolism and the cAMP signaling pathway of P. oryzae, limiting its infection and expansion in host tissues. A pathogenicity test confirmed that RFE-AgNPs significantly reduced disease development in barley and rice leaves. Importantly, RFE-AgNPs displayed significantly lower toxicity to Artemia salina compared with isoprothiolane and commercial AgNPs. CONCLUSION: RFE-AgNPs synthesized using mangrove soil bacterial natural products displayed good control efficacy on rice blast but low ecotoxicity on A. salina and had great potential to be a promising candidate for eco-friendly biopesticides to manage rice blast disease. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.