Isolation and characterization of plant growth promoting rhizobacteria and their biocontrol efficacy against phytopathogens of tomato (Solanum lycopersicum L.)

Plant growth promoting rhizobacteria (PGPR) inhabit the rhizosphere region of plant and often found to be beneficial for the development and growth of plants. In this study, 17 pure isolates of bacteria from the rhizosphere of brinjal (Solanum melongena L.) and chilli (Capsicum annuum L.) were screened for their potential in growth promotion and antagonistic effect towards fungal pathogens of tomato plant (Solanum lycopersicum L.). Among the isolates, two bacterial strains (JB and JC) showed prominent activity and were further investigated. The selected bacterial isolates were identified as Pseudomonas aeruginosa and designated as P. aeruginosa JB and JC. Both the bacterial isolates enhanced the production of plant growth promoting compounds, such as phytohormones and salicylic acid. Seed inoculation with P. aeruginosa JB and JC also significantly improved the germination and growth of S. lycopersicum L. The bacterial strains were found to exhibit significant antagonistic effect towards the tested pathogens, Fusarium oxysporum and Alternaria solani. In the pot experiment, both the bacterial isolates P. aeruginosa JB and JC showed significant efficacy in decreasing the disease severity of test phytopathogens. These results suggested that both the rhizobacterial species could be further exploited as potential bio-inoculants for the improvement of plant growth, productivity and defence against phytopathogens.