Growth stimulation and alleviation of salinity stress to wheat by the biofilm forming Bacillus pumilus strain FAB10

Salinity ranks among the most severe environmental stressors that limit crop productivity. Use of microbial inoculants with desired traits is believed to be effective strategy to combat plant abiotic stress. Therefore, the objective was to isolate salt tolerant Bacillus spp. with multifunctional plant growth promoting traits including biofilm development and to evaluate its performance under salt stress conditions. We isolated and characterized a novel salt tolerant isolate of Bacillus sp. FAB10 with multifunctional traits by screening of 56 selected Bacillus isolates from rhizospheric soils. The isolate FAB10 was identified as B. pumilus based on 16S rRNA gene sequence analysis. The FAB10 isolate produced strong biofilm, enhanced amount of exopolysaccharides, IAA, ACC-deaminase activity and solubilized phosphate in vitro. The isolate FAB10 forms biofilm and expressed its associated traits at the different NaCl concentrations in vitro. Biofilm development on Wheat root surface was also demonstrated at 250 mM salt (NaCl) concentration. Successful root colonization by the FAB10 isolate was demonstrated via scanning electron microscopy and viable counts. Wheat plant var. 343 inoculated with Bacillus pumilus isolate FAB10 grown in the presence of different concentrations (0 to 250 mM) of NaCl under pot house conditions. At elevated concentration of NaCl adverse effect on wheat growth parameters and other biochemical attributes pertaining to photosynthesis, transpiration, and content of proline in plant tissue was recorded in uninoculated plants. However, inoculated plants showed a significant (p < 0.005) improvement in most of the above parameters. Similarly a significant (p < 0.005) reduction in antioxidant enzyme activities (catalase, superoxide dismutase, and glutathione reductase) and malonaldehyde content in wheat was observed in FAB10 inoculated plants than uninoculated plants in the presence of salt. The findings indicated that multifunctional traits of the FAB10 contribute to NaCl stress alleviation in wheat plants through multiple mode of action and it could be exploited under field condition.