Bacillus velezensis SGTSH 0811 suppresses sunflower sclerotiniose by pathogen inhibition and host resistance induction

Abstract Sunflower sclerotiniose caused by Sclerotinia sclerotiorum threatens global sunflower production, the complete molecular antagonistic mechanisms of Bacillus velezensis biocontrol strains are still unclear. This study isolated rhizosphere strain SGTSH 0811 from healthy sunflower soil to evaluate its biocontrol potential and antagonistic mechanisms. The strain exhibited dual beneficial functions: it strongly inhibited S. sclerotiorum growth and sclerotial germination in vitro and achieved stable disease control in field trials. Whole-genome analysis identified 12 secondary metabolite biosynthetic gene clusters, six of which have verified antifungal functions. Mechanistic tests revealed that thermostable lipopeptide metabolites produced by SGTSH 0811 damage the pathogen’s cell wall and membrane, and induce global transcriptional reprogramming to suppress fungal virulence and stress resistance. In addition, SGTSH 0811 promotes sunflower growth, increases antioxidant enzyme activities and proline accumulation to activate host induced resistance. These results reveal the dual synergistic biocontrol mode of SGTSH 0811, and lay a theoretical foundation for developing multi-functional eco-friendly biopesticides against soil-borne sclerotiniose.