Growth and Metabolic Response of Glycine max to the Plant Growth-Promoting Enterobacter Delta PSK and Bradyrhizobium japonicum Under Salinity Stress

This study was designed to test the ability of some plant growth-promoting bacteria to adverse the effects of salinity on soybean growth. The effect of Bacillus MAP3 and Enterobacter Delta PSK, along with Bradyrhizobium japonicum was studied on soybean at two levels of NaCl salinization (50 and 100 mM). The physical growth parameters of bacterized soybean (21 days old), particularly plants co-inoculated with Bradyrhizobium japonicum + Enterobacter Delta PSK, were significantly enhanced compared to control plants. The shoot length, leaf area, root length, and chlorophyll a content increased by 49.58%, 78.58%, 20.19%, and 57.35%, respectively, indicating the promoting activity of this bacterial combination. After 19 days following the onset of salinity stress, the retarded growth parameters in controls improved significantly due to bacterial treatments, especially by Bradyrhizobium japonicum + Enterobacter DeltaPSK, which increased the values of all growth parameters significantly regardless of the salinity level. Additionally, electrolyte leakage, the amounts of malondialdehyde and hydrogen peroxide decreased considerably due to this combined bacterial treatment. Overall, the combination treatment of Enterobacter Delta PSK and the original symbiont B. japonicum enhanced soybean growth under salt stress, indicating the ability of Enterobacter Delta PSK to mitigate osmotic stress. The effect of this strain on soybean yield should be further evaluated to pave the way for its use as a biofertilizer along with B. japonicum, especially under salt stress.