Biogenic Silver Nanoparticles From Rice Seed Endophytes Enhance Growth and Suppress Major Rice Phytopathogens

The bacterial-blight and fungal-blast disease in rice, caused by Xanthomonas oryzae and Magnaporthe oryzae, are the leading causes of rice production loss globally. Excessive reliance on chemical fertilizers and pesticides in agriculture contributes to environmental toxicity; alternatives, like nanoparticles, are safer for plant growth enhancement and disease management. This study focuses on the synthesis of biogenic silver nanoparticles (AgNPs) using beneficial rice-seed endophytic bacterium. Scanning and transmission electron microscopy revealed the spherical nature of the AgNPs with a size range of 10-20 nm. Energy-dispersive X-ray spectroscopy of the AgNPs confirmed the presence of elemental silver, validating the synthesis mechanism. The impact of these biogenic AgNPs on rice growth was investigated through controlled experiments, demonstrating significant enhancement in seed germination and seedling growth of up to 50%. The AgNPs exhibited promising antimicrobial activity against bacterial and fungal pathogens. It has been found that AgNPs can be taken up through rice roots and transported to leaves and shoots. The results further suggest that AgNP treatment induces variable changes in the expression of immunity-related genes in rice. While genes like Oscul3a were downregulated, OsWRKY31 was strongly upregulated, indicating a complex response that could involve both suppression and activation of immune pathways. Both in vitro and in vivo assays revealed substantial antibiosis against Xanthomonas and Magnaporthe, emphasizing their potential as a natural alternative to synthetic antimicrobials. The results highlight their dual functionality in enhancing crop growth and serving as an environmentally friendly solution for controlling agricultural pathogens.