Endophytic bacteria from Ocimum sanctum and their yield enhancing capabilities

Endophytes are beneficial microbes that reside intercellularly inside the plants. Interaction of endophytes with the host plants and their function within their host are important to address ecological relevance of endophyte. Four endophytic bacteria OS-9, OS-10, OS-11, and OS-12 were isolated from healthy leaves of Ocimum sanctum. These isolated microbes were screened in dual culture against various phytopathogenic fungi viz. Rhizoctonia solani, Sclerotium rolfsii, Fusarium solani, Alternaria solani, and Colletotrichum lindemuthianum. Of these, strain OS-9 was found to be antagonistic to R. solani, A. solani, F. solani, and C. lindemuthianum while OS-11 was found antagonistic against A. solani only. The growth-promoting benefits of the endophytes were initially evaluated in the glasshouse by inoculated seeds of O. sanctum. Treatment with endophytes OS-10 and OS-11 resulted in significant enhancement of growth as revealed by increase in fresh as well as dry weight. Further, field trials involving two genotypes OS Purple and CIM-Angana were conducted with strains OS-10 and OS-11. The growth-promoting effect was visible on both the genotypes tested as the endophytes significantly enhanced fresh herbage yield (t/ha). Interestingly, these endophytes increased the content of essential oil particularly in cultivar OS Purple and thereby increasing the total oil yields. Molecular characterization of strain OS-11 indicated the strain to be highly related to the type strain of Bacillus subtilis.