Isolation and Identification of Bacterial Isolates from Saline Soil and Evaluation of Plant Growth-Promoting Traits under Salt Stress

Stenotrophomonas spp., identified as rhizospheric bacteria, demonstrate considerable potential in enhancing plant growth under saline stress via mineral solubilization and the synthesis of bioactive metabolites. This study involved the acquisition of bacterial isolates from salt-affected soils, which were then subjected to thorough morphological, biochemical, and molecular characterization. Molecular identification was performed through amplification and sequencing of the 16S rRNA gene; analysis of the resultant sequences verified the isolates as Stenotrophomonas rhizophila. The sequences have been deposited in the GenBank database with accession numbers PQ438080 (strain SprA) and PQ438113 (strain SprB). Both isolates displayed optimal growth at 37 °C and exhibited extensive tolerance to salinity, pH, and temperature, sustaining viability up to 50 °C. Functional assays demonstrated their capacity to solubilize phosphate and synthesize siderophores, indole-3-acetic acid (IAA), and hydrogen cyanide (HCN). Strain SprA demonstrated superior growth efficiency across various NaCl concentrations (OD₆₀₀: 0.112–0.900), whereas strain SprB achieved the highest IAA production (83.73 µg/mL). The physiological and biochemical characteristics, along with their established taxonomic classification, highlight the potential of S. rhizophila strains as bioinoculants for improving plant resilience and productivity in saline agroecosystems.