THE MITIGATION OF SALT-STRESS OF VIGNA RADIATA (L.) BY AUXIN-PRODUCING SALT-TOLERANT RHIZOBACTERIA

Abstract Halotolerant microorganisms have the ability to mitigate the deleterious impacts of salinity on the plant’s physiological attributes. The major objective of this study was to evaluate the bacterial diversity associated with Suaeda fruticosa (Forssk L.) growing in saline soils. Salt-tolerant bacteria were screened for their potential to promote the growth of Vigna radiata under saline conditions. Bacterial strains isolated in this study were found to tolerate NaCl up to 1.5M. These strains were found positive for the production of indole-3 acetic acid (IAA), HCN production, cellulose activity, nitrate reduction, and nitrogenase activity. 16S rRNA sequencing showed that strains belong to eight different bacterial genera including Brachybacterium, Oceanobacillus, Halomonas, Microbacterium, Kushneria, Kocuria, Rothia, and Staphylococcus. Bacterial strain Halomonas caseinilytica DO, Halomonas elongate S3W and Oceanobacillus picturae Ra6S3 showed 70.46 µg/ml, 113.53 µg/ml and 73.25 113.53 µg/ml of auxin production under 1M salinity stress in the presence of 1000 µg/ml of L-tryptophane whereas, at 1.5M salinity stress Halomonas elongate S3W showed 93.17 113.53 µg/ml of IAA production. In pot trials with Brachybacterium paraconglomeratum (Ra11S4), Staphlococcus equorm (Rb8S4), Rothia endophytica (Rb2S6) recorded increases in fresh biomass up to 2.4 folds and number of pods up to 2.1folds for the plant Vigna radiata. These strains can be used as promising bacterial inoculants in sustainable agriculture for the mitigation of salinity stress.