Phosphate-Solubilizing Salt-Tolerant Bacteria to Support Soybean Growth (Glycine max (L.) Merr.) On Saline Soils

Phosphorus is one of the important elements of plant nutrition that affect crop productivity. Increasing the availability of phosphorus through the use of microbial inoculants capable of stimulating soybean growth on saline soils is a promising solution to the problem. However, most phosphate-solubilizing bacteria are not capable of the growth and mobilization of phosphates on saline soils. The purpose of this study was to isolate phosphate-solubilizing salt-tolerant bacteria from the soybean rhizosphere and to study their salt tolerance, phosphate solubilization, and ability to influence soybean growth in saline soils. Phosphate-solubilizing isolates were obtained from the soybean rhizosphere. Their ability to grow and mobilize phosphates under conditions of high salt stress was studied, after which five strains were selected. Identification by the Sanger molecular genetic method showed that the strains were Pseudomonas rhizosphaerae FT2, Ps. koreensis FT4, Ps. sp. FM9, Bacillus pumilus FM12, and B. sp. FC11. The production of the phytohormone indole-3-acetic acid under high salt stress was studied and three strains (FT4, FM12, and FC11) were selected in which the production of indole-3-acetic acid under salt stress decreased slightly by 20-22%. Inoculation with bacteria significantly mitigated salt stress, as evidenced by the growth indicators of soybeans; the weight of roots increased by 1.9-2.1 times, the weight of soybean shoots by 2.0-2.2 times, the weight of leaves by 2.5-3.5 times and the number of nodules by 1.7-2.0 times compared to the control variant without inoculation. The study showed that inoculation with phosphate-solubilizing salt-tolerant bacteria increased plant resistance to salt stress, improved growth, and promoted the ecological adaptation of soybeans. Based on the isolated strains, it is possible to develop inoculants for crops growing on saline soils, which is a promising strategy.