Biocontrol of Bacterial Wilt Biotic Stress in Tomato Plants by Successful Host Root Colonization and Inducing Host Resistance

Plant treatments with biocontrol agents to deal with biotic stress are widely reported, but the information regarding detailed action mechanisms of biocontrol and host response is rarely reported. This study investigated a biocontrol bacterial agent, Bacillus cereus, to manage tomato bacterial wilt (BW) disease. The in vitro antibacterial potential of B. cereus was assessed, followed by the ability of B. cereus to colonize tomato roots and induce host resistance. Additionally, we tested the application of B. cereus for managing tomato BW disease. In vitro investigations revealed the volatile mediated antibacterial activity of B. cereus, indicating that B. cereus produces antibacterial volatiles against R. solanacearum. The effectiveness of B. cereus in colonizing tomato roots was evaluated through its transgenic GFP-tagged strains and confirmed through qPCR analysis. It was found that the biocontrol bacterium successfully colonized the host root. The B. cereus concentration reached 9.37 × 107 at 48 h. The tomato plants under bacterial wilt stress, when treated with B. cereus, showed upregulation of genes linked to the plant defense system. The application of B. cereus to soil infested with R. solanacearum and planted with tomato plants reduced the pathogen population in the soil, resulting in a reduction in disease severity and improved plant growth. This study suggests the biocontrol potential of B. cereus to manage bacterial wilt disease.