Biosynthesized selenium nanoparticles increase soybean resistance to root rot by recruiting beneficial microbes and...

Soybean root rot, primarily caused by Fusarium species, is a devastating soil-borne disease that severely threatens global soybean production. Conventional chemical controls are problematic due to their environmental impact and the risk of fostering pathogen resistance. There is therefore an urgent need to develop sustainable and eco-friendly alternative strategies.

This study demonstrated that selenium nanoparticles (SeNPs) biosynthesized by Bacillus subtilis ZY56 significantly increased soybean resistance to F. oxysporum. Characterization confirmed that the obtained SeNPs were spherical (approximately 147 nm), consisting of amorphous-state elemental selenium (Se⁰) with a bioactive protein-polysaccharide coating. Treatment with 2.66 mg/L SeNPs significantly promoted seed germination, seedling growth, and antioxidant enzyme activity, while markedly reducing the root rot disease index. Multiomics analyses revealed that SeNPs reprogrammed host metabolism by increasing the levels of key defense-related metabolites (camalexin and isoflavonoids) and upregulating associated biosynthetic pathways. Crucially, SeNPs reshaped the rhizosphere microbiome, enriching beneficial genera (e.g., Bradyrhizobium, Lysobacter, and Nocardioides). Moreover, the analysis predicted enhanced microbial tyrosine metabolism. Integrated correlation analysis identified tyrosine metabolism as a core hub linking microbiome restructuring to host defense, supporting a "microbe‒plant metabolic division of labor" model in which microbes supply precursors (e.g., L-tyrosine) for the synthesis of antifungal compounds in the host. This finding was functionally validated, as the accumulated metabolites (camalexin and isoflavonoids) directly inhibited F. oxysporum growth in vitro.

Our findings reveal a dual mechanism whereby SeNPs concurrently prime host defenses and modulate beneficial plant-microbe interactions, offering a sustainable nano-enabled strategy for managing soil-borne diseases. Video Abstract.