Halotolerant Bacteria Enhanced Resilience to Salinity Stress Through Modulating Stress-Responsive Gene Expression in Wheat

Purpose. Soil salinization of arable lands significantly threatens sustainable crop yields and global food security. Halophyte-rhizosphere indigenous bacteria demonstrated promising potential to enhance the plant performance under salinity stress in the present study. Methods. Ten halotolerant bacterial isolates (P1 to P10) were isolated from the roots of halophytes (Suaeda maritima, Aeluropus lagopoides and Salicornia brachiata) growing at intertidal coastal soils of Gujarat, India. After screening for plant growth-promoting (PGP) activities, these isolates were tested for their ability to promote growth and develop salt tolerance in wheat (Triticum aestivum) under salinity (150 mM NaCl). Biochemical parameters and gene expression profiling of 10 stress-related genes, encompassing salt overly sensitive (SOS) pathways, ion transporters, and antioxidant enzymes were analyzed. Results. These bacterial isolates belonged to diverse genera, including Bacillus, Azospirillum, Herbaspirillum, Brachybacterium, Klebsiella, Aeromicrobium, Microbacterium, Aeromonas and Flexivirgo. Inoculation with halotolerant plant growth-promoting rhizobacteria (PGPR) significantly improved the plant growth attributes, including chlorophyll and protein levels and water retention in wheat under salt stress (150 mM NaCl) in contrast to the control plants. The inoculated seedlings exhibited elevated antioxidant enzymatic potential, accompanied by reduced malondialdehyde levels and decreased electrolyte leakage under salt stress. Notably, the PGPR strains P2, P6, P9, and P10 demonstrated comparatively higher expression levels across most target genes associated with antioxidant defense and ion transport. Salt stress-induced enhancements in the nutrient content were strongly associated with microbial stimulation of soil enzyme activities. Conclusion. These observations suggest the possibilities of halotolerant PGPR as a potent bioinoculant for enhancing wheat production in saline soils through the modulation of antioxidant enzyme genes and salt-responsive transport systems.