Use of silver nanoparticles for managing Gibberella fujikuroi on rice seedlings

• Silver nanoparticles reduced viability of Gibberella fujikuroi.
• Silver nanoparticles disinfected rice seeds infested on the surface with G. fujikuroi.
• Silver nanoparticles improved seedling emergence and height of G. fujikuroi-infested rice seeds.
• Silver nanoparticles caused no adverse effects on seed germination or seedling growth.
• Silver nanoparticles are a new ingredient for seed treatment.

It is of great interest for rice producers to develop novel seed disinfection methods with effective, less toxic, and environment-friendly active ingredients. This study evaluated silver nanoparticles (AgNP) as an alternative agent for seed treatment since elemental silver possesses strong antimicrobial properties and a low toxicity to humans and animals. AgNP (∼7.5 nm in diameter) solution was chemically synthesized and evaluated for antifungal activity against Gibberella fujikuroi as representing a seedborne fungal pathogen in rice (Oryza sativa). AgNP reduced viability of G. fujikuroi conidia by 50% when directly exposed to concentrations ranging from 0.015 to 1.5 μg mL−1 for 1 to 20 min. Rice seeds infested with G. fujikuroi and treated with 150 μg mL−1 of AgNP significantly decreased colony-forming units (CFU) of G. fujikuroi on the seed surface when treated for 10 min and up to 24 h. Seed treatment with 150 μg mL−1 AgNP for 12 or 24 h significantly improved seedling emergence and height of G. fujikuroi-infested seeds. Adverse effects on germination rate and seedling growth were not observed with any of the AgNP treatments (≤150 μg mL−1 for up to 48-h exposure) tested in this study. The antifungal effect of AgNP against G. fujikuroi attested in this study suggests that AgNP is a new antifungal ingredient that can be used for managing important seedborne fungal pathogens of rice.