Isolation and Characterization of Halotolerant Plant Growth-Promoting Rhizobacteria for Sustainable Agriculture in...

This study aimed to isolate, identify, and functionally characterize halophilic plant growth-promoting rhizobacteria (PGPR) from saline soils as candidates for sustainable biological strategies to enhance crop productivity in saline environments. This work represents an early-stage screening effort to identify promising bacterial strains for subsequent field evaluation. Fourteen halotolerant bacterial isolates were recovered from saline soils and identified using morphological, biochemical, and molecular approaches. The most promising strains belonged predominantly to the Enterobacteriaceae family, including Pantoea agglomerans, Enterobacter cloacae, Enterobacter cancerogenus, and Enterobacter kobei. Functional characterization revealed diverse plant growth-promoting capabilities, including sugar fermentation, organic acid production, ammonia and indole-3-acetic acid (IAA) synthesis, exopolysaccharide and siderophore production, and phosphate solubilization. Phosphate solubilization indices ranged from 2.08 to 3.04 cm, corresponding to soluble phosphate concentrations of 878-1483 µg mL⁻¹, while IAA production varied between 4.067 and 23.410 µg mL⁻¹. Notably, these strains exhibited dual capacity for high salt tolerance (surviving in media with > 8% NaCl) and efficient siderophore production (up to 63%), which is crucial for iron acquisition under saline stress. In barley seed germination assays, inoculation with Enterobacter cloacae strain AZ8 significantly enhanced germination to 80%, compared to 40% in the uninoculated control. These findings identify E. cloacae AZ8 as a promising candidate for further development as a bioinoculant to improve seed germination and early plant vigor in saline soils. This study provides foundational knowledge supporting the development of biological strategies for sustainable crop production in salt-affected agricultural systems, though field validation and safety assessments would be required before commercial deployment.