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ABSTRACT
The aim of this study was to investigate the effect of Cr(VI) on the plant growth-promoting traits of potential rhizobacterial strain isolated from Phaseolus vulgaris rhizosphere. A total of 36 rhizobacterial strains were recovered from the rhizosphere of P. vulgaris. Among these strains, the strain AR8 was specifically selected due to the highest resistance against heavy metals and the maximum production of plant growth-promoting substances. The rhizobacterial strain AR8 was identified as Cellulosimicrobium funkei (KM263188) following 16S rDNA gene sequencing. Strain AR8 solubilized phosphate and produced indole-3-acetic acid (32.57 µg/ml), exopolysaccharide (17.23 µg/ml), ammonia (54.16 µg/ml), catalase, biosurfactant, protease, amylase, and lipase. Under Cr(VI) stress, Cr(VI) concentration-dependent progressive decline in all plant growth-promoting traits of the C. funkei exposed was observed except for exopolysaccharide production, which consistently increased with increasing concentrations of Cr(VI). The root elongation assay resulted that the application of C. funkei strain AR8 significantly increased root length of test crops both in the presence and absence of Cr(VI) compared to uninoculated Cr(VI) treated plants. Moreover, AR8 generated a large number of colonies in diverse agricultural crops. Due to these intrinsic abilities, strain AR8 could be utilized for growth promotion as well as for the remediation of chromium in chromium-contaminated soil.
Acknowledgments
The authors would like to express their heartfelt thanks to Plant and Microbial Biotechnology laboratory members for their immense help and Department of Biotechnology, Periyar University, Salem, Tamil Nadu, India, for providing laboratory facilities.