Damping-off and collar rot is one of the most important diseases of cowpea causing great menace in cowpea production. Application of chemical fungicides is still being a commonly used approach and rules among all the management approaches. Continuous and non-judicious application of chemical fungicides not only causes environmental hazards and residual toxicity related problems but also may trigger fungicide resistance problem. Disease containment through ecofriendly biocontrol approach, using natural antagonistic plant growth promoting rhizobacteria (PGPR) is now becoming an inevitable component in the integrated management strategy of the disease. Thus, research study was conducted to isolate and evaluate the potent native plant growth promoting rhizobacteria (PGPR) isolates, their potential use for improving growth, yield and management of damping off disease in cow pea. Six potent PGPR strains were isolated and studied for their plant growth promotion, their molecular identification at genus level and management of damping off disease in cowpea. All of the PGPR isolates influenced cowpea growth characteristics. Application of PGPR strains significantly increased root and shoot length, root and shoot biomass by 5.4–53.4%, 9.8–48.6% and 10.8–64.5% and 27.8–103.8% respectively, over the un-inoculated control. Among the six potent PGPR strains Hu3, Hu4, Hu9, Hu14, Hu18 and Hu19; Hu3, Hu18 and Hu19 rhizobacterial isolates were found to be the most effective isolates for rhizosphere competence and plant growth promotion of cowpea seedlings. Also, these isolates Hu3 and Hu18 were more effective in suppressing the pre & post emergence incidence of damping off as compared to other rhizobacteria. The seed and soil treatment with Hu3 and Hu18 rhizobacteria recorded minimum pre-emergence damping-off disease of 5.56 percent in comparison to control. The seed and soil treatment with Hu3 recorded significantly least post-emergence damping off (13.78 percent) comparison to control pot having 50% damping off. The seed and soil treatment with Hu3 recorded significantly maximum (5.33 cm) root length and Hu18 isolate recorded significantly maximum shoot length (21.07 cm) compared to sick pot. Molecular characterization of these isolates showed that these native PGPR rhizobacteria Hu3, Hu9, Hu14, Hu18 and Hu19 were identified as Bacillus spp. based on Bacillus spp. specific primers. The bacterial bioagents Hu3, Hu18 and Hu19 showed effective results in reducing pre- and post-emergence damping-off disease in S. rolfsii pathogen infested soils and also may lead to more seedling vigour and also application of these PGPR rhizobacterial isolates could be a viable supplementary strategy for field level application for maximum benefits through alleviation of biotic stresses and enhancing sustainable crop production.

Plant growth promoting rhizobacteria (PGPR), Damping off disease, Plant health management

The results of this study clearly indicate that Hu3, Hu18 and Hu19 PGPR rhizobacterial isolates were found to be the most effective isolates for rhizosphere competence and plant growth promotion of cowpea seedlings and incase of damping off pathogen disease suppression, Hu3 and Hu18 rhizobacteria found to be excellent bacterial bioagents for successful management of this soil borne phytopathogen. This study has extended the range of the PGPR strains that have promising results and it can be used as biocontrol agents to alleviate plant disease stress further increasing crop productivity.

Huma Nazneen, Emmadi Venu, Krishnendu Sen, Ritesh Kumar, Krishna Ray, Ashish Roy Barman, S.K. Ray, Raghunath Mandal and Subrata Dutta (2022). Efficient Native Plant Growth Promoting Rhizobacteria and their Role in Plant Growth Promotion and Management of Damping off Disease in Cowpea. Biological Forum – An International Journal, 14(4a): 148-154.