Bacillus velezensis SGTSH 0811 controls sunflower sclerotiniose by targeting the pathogen and priming the host

Background Sunflower sclerotiniose, caused by the fungal pathogen Sclerotinia sclerotiorum, is a devastating disease that results in substantial yield losses in sunflower production globally, highlighting an urgent need for sustainable and eco-friendly management strategies. Bacillus velezensis has emerged as a promising biocontrol agent against various plant fungal pathogens due to its safety and effectiveness, however, the specific molecular mechanisms underlying its antagonistic effects against S. sclerotiorum remain poorly understood, which limits its widespread application in sunflower sclerotiniose control. Results A novel B. velezensis strain, SGTSH 0811, was isolated from the rhizosphere soil of healthy sunflowers, and its biocontrol potential and growth-promoting effects were systematically evaluated. The strain exhibited potent dual-function biocontrol activity: in vitro experiments demonstrated significant antifungal inhibition against S. sclerotiorum, while field trials confirmed its excellent control efficacy against sunflower sclerotiniose. Genomic analysis of SGTSH 0811 identified 12 biosynthetic gene clusters (BGCs), among which 6 were annotated to possess known antimicrobial functions, providing a genetic basis for its antifungal activity. Further in vitro studies showed that the cell-free filtrate of SGTSH 0811 could disrupt the structural integrity of S. sclerotiorum, leading to plasma membrane leakage, cell wall damage, hyphal deformation, and ultimately pathogen cell death. Transcriptomic profiling of S. sclerotiorum treated with SGTSH 0811 metabolites revealed 216 differentially expressed genes, which clearly indicated that the strain induces metabolic reprogramming in the pathogen, thereby impairing its pathogenicity and stress adaptation capabilities. Additionally, antifungal lipopeptides isolated from SGTSH 0811 exhibited exceptional antifungal activity and high thermal stability, further confirming the strain’s biocontrol potential. Notably, SGTSH 0811 also exerted significant plant growth-promoting effects on sunflowers, including enhancing stress tolerance by increasing proline content and the activities of antioxidant enzymes. Conclusion The novel B. velezensis strain SGTSH 0811 possesses multi-faceted advantages, including potent antifungal activity against S. sclerotiorum, effective field control of sunflower sclerotiniose, and significant promotion of sunflower growth and stress tolerance. These findings not only present SGTSH 0811 as a promising multi-talented biocontrol candidate for sunflower sclerotiniose management but also provide novel insights into the molecular interplay between Bacillus species and S. sclerotiorum, laying a foundation for the further development and application of biocontrol agents.