Isolation and characterization of halotolerant bacilli from chickpea (Cicer arietinum L.) rhizosphere for plant growth promotion and biocontrol traits

The present study describes the identification and polyphasic characterization of salt tolerant bacilli displaying plant growth promoting and broad spectrum antifungal activities. A total of 110 strains were isolated, out of which nine were selected on the basis of halotolerance, in vitro plant growth promoting attributes and antagonism against multiple phytopathogens. Preliminary identification of strains was done on the basis of phylogenetic analysis and comparison of 16S RNA sequences with type strains. The test strains were identified as Bacillus pumilus, B. subtilis, B. licheniformis, B. safensis and B. cereus. These strains possess ability to tolerate high salt (8-10% NaCl), form endospore, showed broad spectrum antifungal activity and therefore might cope with adverse environments. Scanning electron microscopy of promising test strains (CG18 and CM25) and pathogen interaction indicated destruction of fungal mycelia by halotolerant antagonists due to cytoplasmic extrusion. Moreover, PCR amplification of bacillomycin (bmyB), chitinase (ChiA), and -glucanase genes and production of hydrolytic enzymes suggested that test strains could have a role to manage plant pathogens under saline conditions. Finally, the selected strains exhibited some plant growth promotion traits. Overall, this study demonstrated that the evaluated strains could be useful in developing microbial products to enhance tolerance to biotic and abiotic stresses and boost plant growth.