Intervention of antagonistic bacteria as a potential inducer of disease resistance in tomato to mitigate early blight

Early blight (EB), caused by Alternaria solani, is one of the major threat that limiting tomato production globally. Microbial biopesticides derived from bacteria have the potential to produce a wide range of antifungal metabolites with remarkable biocidal effects. In vitro screening with twenty bacterial strains was carried out by a dual-culture assay, amongst three strains of Bacillus subtilis (BS-01, BS-02 and BS-03), one each of Pseudomonas maltophilia (PM-01) and Azospirillum brasilense (AB-01) were selected as potential antagonists for in vivo assay. Results of pot experiment revealed that foliar application of antagonists significantly managed EB disease by 42-92% with a notable reduction in disease percent severity index by 10-60% and improved the plant growth attributes by 25-165%. Induction of resistance in tomato plant was triggered by up regulation of antioxidant enzymes viz., catalase, peroxidase and polyphenol oxidase along with the high production of total phenolics. Biocontrol efficacy on tomato fruit indicated that BS-01 also proved effective in managing percent infection severity by 60%. The results of current investigation suggested that BS-01 (B. subtilis) was found to be as an excellent resistance inducer in plants that could be used as biopesticides as a prospective management tool against EB disease of tomato.