Unveiling the role of Lysinibacillus sphaericus in plant growth promotion, hydrolytic enzyme activities and biocontrol efficacy against Rhizoctonia solani

Rhizoctonia solani is a destructive soil-borne fungal pathogen affecting diverse crops due to its persistent sclerotia and aggressive spread. Chemical control poses risks of toxicity and non-target effects. As a sustainable alternative, Lysinibacillus sphaericus, a Gram-positive, spore-forming bacterium, shows promise due to its toxin production, plant growth-promoting (PGP) traits, and antagonistic activity. In this study, 25 L. sphaericus strains were isolated and characterised morphologically, microscopically, and through 16S rRNA gene sequencing. Phylogenetic analysis revealed two major clades, indicating limited genetic diversity. All strains produced indole-3-acetic acid and ammonia; 68% showed siderophore activity. Enzymatic assays indicated protease (80%), lipase (86%), lecithinase (68%), and chitinase (36%) activity. Selected strains were evaluated for antifungal activity against R. solani. Strain NBAIR_LS55 showed significant inhibition in dual culture (70%), poison food (95%), and VOC (97.5%) assays. These results highlight L. sphaericus, particularly NBAIR_LS55, as a multifunctional biocontrol agent and PGP bacterium for sustainable crop protection.