Plant growth-promoting rhizobacteria: Potential improvement in antioxidant defense system and suppression of oxidative stress for alleviating salinity stress in Triticum aestivum (L.) plants

Plant growth-promoting rhizobacteria (PGPRs) can suppress salt stress effects and improve plant productivity. This study elucidated the mechanisms of growth medium-inoculated PGPRs (Bacillus cereus, Serratia marcescens, and Pseudomonas aeruginosa), which contribute to improving salinity tolerance in Triticum aestivum plants grown under two NaCl-salinity levels (150 and 300 mM). The objective was to assess the impacts of soil-inoculated PGPRs on physiological attributes, antioxidant system activities, and their implications for growth and productivity of wheat plants in a pot study. Salinity levels markedly decreased growth and output traits, photosynthetic pigments, gas exchange, membrane stability, plant water content, K+ and Ca2+ contents, and K+/Na+ ratio. While, proline and soluble sugars contents, Na+ and oxidative stress biomarkers (e.g., O-2(center dot-) and H2O2), and antioxidant activities were increased by salinity compared to control. The adverse effects were more pronounced with 300 mM NaCl. However, PGPRs detoxified salinity stress effects and significantly im(p)roved all physiological attributes and further elevated antioxidant activities, while significantly reduced levels of Na+ and oxidative stress biomarkers, which were reflected in significant elevations in plant growth and production. These improvements using PGPRs were better under 150 mM NaCl. The growth-enhancing traits of these halo-tolerant PGPRs like indole-3-acetic acid (IAA) and hydrogen cyanide (HCN) productions, N-2-fixation, and P solubilization, reported in this investigation not only helped wheat plants withstand salt stress but also facilitated their growth under varying concentrations of salts. Thus, the use of PGPRs can be an effective strategy to boost wheat growth and production in salt-affected areas.