Biocontrol efficacy and plant growth promoting activity of Bacillus altitudinis isolated from Darjeeling hills, India.

A total of 18 bacterial isolates were obtained from the rhizosphere of Sechium edule growing in the lower foothills of Darjeeling, India. The bacterial isolates were tested for PGPR traits in vitro such as phosphate solubilization, HCN, siderophore, IAA, chitinase, protease production as well as inhibition of pthytopathogens. Of all the bacterial isolates, one bacterium designated as BRHS/S-73 was found to possess all the tested characters which was identified on the basis of 16S rRNA gene sequence analysis as Bacillus altitudinis and was selected for in vivo studies. A significant improvement in growth measured in terms of increase in root length, shoot length, and increase in root and shoot biomass was observed when seeds of Vigna radiata, Cicer arietinum, and Glycine max were bacterized prior to sowing in field condition. Besides, the bacterium could also solubilize soil phosphate. Apart form growth promotion, root rot disease of Vigna radiata caused by Thanatephorus cucumeris was also significantly reduced by 74% when the bacterium was applied to the rhizosphere prior to pathogen challenge. The biocontrol efficacy of the bacterium was found to be 66.6% even after 30 days of pathogen inoculation. Activities of key defense related enzymes such as phenylalanine ammonia lyase, peroxidase, β-1,3-glucanase, and chitinase in both roots and leaves of treated plants were also enhanced. Results clearly suggest that B. altitudinis (BRHS/S-73) is a potential PGPR which can be used as efficient microorganism for enhancement of plant growth and suppression of fungal disease.