Halotolerant Plant Growth-Promoting Rhizobacteria Induce Salinity Tolerance in Wheat by Enhancing the Expression of SOS Genes

Soil salinity is one of the main yield-limiting factors in various crops. Under different environmental stresses, many rhizobacteria have demonstrated encouraging role in enhancing plant growth and tolerate stress conditions. In this study, three potential 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase- and exopolysaccharides (EPS)-secreting bacterial strains including Bacillus megaterium, B. tequilensis, and Pseudomonas putida have been assessed for their growth-promoting characteristics. These bacterial strains positively affected the physiology, biochemistry, and antioxidant enzymatic activities of wheat plant, under salinity stress. Results of this study depicted that the inoculation of PGPR positively invigorates growth attributes like relative water content and photosynthetic pigments of wheat seedling under saline conditions. Moreover, plants inoculated with PGPR also showed decreased concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2). Inoculation of PGPR reduced electrolytic leakage and enhanced enzymatic activity for the scavenging of reactive oxygen species (ROS). These PGPR also increased the production of proline and total soluble sugar. Expression analysis of selected genes by qPCR revealed higher expression of Salt Overly Sensitive (SOS1 and SOS4) genes and predicted their potential role in stress tolerance. These genes can be further overexpressed in wheat plant to tolerate salinity stress. On the basis of these findings, it can be concluded that the priming of seeds with aforementioned PGPR can decrease the adverse effects of salinity on wheat plant.