Sclerotinia stem rot (SSR), a soil-borne plant disease, cause the yield loss of oilseed rape. Selenium (Se), a beneficial element of plant, improves plant resistance to pathogens, and regulates microbial communities in soil. Soil microbial communities has been identified to play an important role in plant health. We studied whether the changes in soil microbiome under influence of Se associated with oilseed rape health. SSR disease incidence of oilseed rape and soil biochemical properties were investigated in Enshi district, “The World Capital of Selenium”, and soil bacterial and fungal communities were analyzed by 16S rRNA and ITS sequencing, respectively. Results showed that Se had a strong effect on SSR incidence, and disease incidence inversely related with plant Se concentration. Besides, soil Se enhanced the microbiome diversities and the relative abundance of PGPR (plant growth promoting rhizobacteria), such as Bryobacter, Nitrospirae, Rhizobiales, Xanthobacteraceae, Nitrosomonadaceae and Basidiomycota. Furthermore, Soil Se decreased the relative abundance of pathogenic fungi, such as Olpidium, Armillaria, Coniosporium, Microbotryomycetes and Chytridiomycetes. Additionally, Se increased nitrogen metabolism, carbohydrate metabolism and cell processes related functional profiles in soil. The enrichment of Se in plants and improvement of soil microbial community were related to increased plant resistance to pathogen infection. These findings suggested that Se has potential to be developed as an ecological fungicide for biological control of SSR.

There is a pressing need for new nanomaterials for multipurpose functions. The biological synthesis of nanoparticles is environment-friendly, least toxic, and cost-effective. An experiment was designed to use extracellular amylases in the cell-free filtrate (CFF) for the biosynthesis of silver nanoparticles (AgNPs) from the Trichoderma harzianum MTCC 801 strain. Potato dextrose broth (PDB) as general-purpose growth media and amylase production media (APM) as enzyme-specific production media have been used for sub-merged fungal cultivation and nanoparticle synthesis. AgNPs synthesized in the CFF of PDB were compared with AgNPs synthesized from the CFF using APM. The cell-free filtrate obtained upon enzyme stimulation has contributed to the reduction and capping process of nanosilver. The synthesized AgNPs showed a spectral peak at 420 nm, a characteristic feature of AgNPs. The particles were monodispersed, 50 nm in size, and spherical in shape as well as have shown an antifungal effect (100% inhibition) against Sclerotinia sclerotiorum MTCC8785. This is the first report to synthesize trichogenic AgNPs using extracellular amylases against the phytopathogen Sclerotinia strain.