Isolation and Identification of PGP Rhizobacteria from Saline Soils and Their Effect on Nutrients Uptake in Wheat under Salinity Stress

This study was carried out to isolate and identify plant growth-promoting rhizobacteria (PGPR) from saline soils and to evaluate the effect of isolated rhizobacteria, as well as symbiotic and endophytic fungi on the concentration of some nutrient elements in wheat plants under salinity stress in greenhouse conditions. Factors included microbial treatments (rhizobacteria, mycorrhizal fungi, endophytic fungus, and control) and salinity levels (no salinity, 8 and 14 dS m-1). At the end of the growth period, the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), zinc (Zn) and manganese (Mn) in the shoot of the wheat plant, as well as the percentage of root colonization were measured. Based on growth-promoting trails, three isolates among the ten purified rhizobacteria were selected for phenotypic and molecular identification. Two identified isolates belonged to Pseudomonas genus (Pseudomonas aeruginosa Ur743 and Pseudomonas fluorescens Ur745), and the last one was Stenotrophomonas maltophilia Ur840. When the concentrations of nutrient elements were at the non-salinity level, mycorrhizal fungi were better than other microbial treatments in terms of absorbing P, Fe, and Mn, However, at the highest salinity level (i.e., 14 dS m-1), rhizobacteria significantly improved concentrations of N, P, Fe, and Mn in the plant shoot, compared to the control. Besides, the PGP bacteria increased the concentrations of K and Zn, as well as K:Na ratio by 1.99, 1.71, and 1.37 times, respectively, as compared to the control. In general, native microorganisms isolated from saline soil, as compared to other microorganisms in this study, improved the nutrient uptake and increased the wheat plant biomass under salinity stress.