Unveiling the Genomic Basis of Antagonism and Plant Growth Promotion in the Novel Endophyte Bacillus velezensis Strain B.B.Sf.2

Background/Objectives: The agriculture sector faces significant challenges due to global climate change, environmental stressors, and rapid population growth, compounded by unsustainable farming practices. This study investigates the potential of the endophytic bacterial strain B.B.Sf.2, isolated from the bark of Salvia fruticosa and identified as Bacillus velezensis through phylogenomic analyses. Methods: To address these issues, eco-friendly techniques, such as the application of plant-associated microbes, are gaining attention. Genome mining revealed numerous secondary metabolite biosynthetic gene clusters associated with plant growth promotion, biocontrol, colonization, and defense elicitation. Results: The strain exhibited strong antagonistic activity against phytopathogens, mediated by diffusible and volatile compound production, along with plant-growth-promoting traits and environmental adaptability. Genome mining revealed numerous secondary metabolite biosynthetic gene clusters associated with plant growth promotion, biocontrol, colonization, and defense elicitation. B.B.Sf.2 effectively inhibited Colletotrichum species causing olive anthracnose and suppressed Botrytis cinerea, the gray mold pathogen, in post-harvest studies on infected fruits. Bioautography of ethyl acetate extracts demonstrated bioactivity against B. cinerea, attributed to iturin-like metabolites. The extracts maintained bioactive properties regardless of fungal interaction. Furthermore, the strain significantly promoted the growth of Arabidopsis thaliana via diffusible and volatile compounds. Conclusions: Our results highlight the multifunctional potential of B.B.Sf.2 as a biocontrol and growth-promoting agent, warranting further evaluation in field applications to enhance sustainable agriculture.