From grass to legume: employing Poa pratensis-associated bacteria to improve soybean performance under salinity...

Soil salinity is one of the major abiotic stresses limiting agricultural productivity worldwide, and strategies to enhance plant tolerance are of critical importance. Soybean (Glycine max) is a globally important legume crop, providing a vital source of protein for human consumption and livestock feed, as well as serving as a raw material for various industrial products. In this study, endophytic bacteria were isolated under two temperatures (5 °C and 28 °C) in TYE media from the roots of Poa pratensis. Preliminary screening for plant growth-promoting activity was performed using a soybean germination assay under salt stress conditions (0, 75, 100 mM NaCl). Among the isolates, two strains showing the most pronounced positive effects on germination rate and percentage were selected for molecular identification. Phylogenetic analysis of 16S rRNA gene sequences with bootstrap support demonstrated that both isolated strains belong to the genus Pseudomonas. The growth of these strains was monitored in saline media and demonstrated tolerance up to 500 mM NaCl. Biochemical characterization showed their ability to produce auxins, siderophores, and solubilize phosphate. In pot experiments, soybean seeds were inoculated with these strains, and salinity stress was applied 24 hours after inoculation. The results demonstrated that the inoculated plants exhibited improved growth under salt stress, including enhanced root development, greater dry biomass accumulation, and increased overall vigor. These findings suggest that Pseudomonas endophytes isolated from Poa pratensis possess potential, as bio-inoculants, to mitigate the adverse effects of salinity and promote sustainable soybean cultivation.