Combination of Graphene Oxide and Rhizobium Improved Soybean Tolerance in Saline-Alkali Stress

Soybean (Glycine max L.) is the most important crop plant in the world. Soil saline-alkali seriously inhibits soybean yield and quality. This study aims to investigate the impact of graphene oxide (GO) and Rhizobium (Rh) on the expression of soybean-related genes as well as the growth and yield under saline-alkali stress. The results show that GO + Rh-treated increased the number of root nodules by 5.43 times compared with the control (Ctrl), the total nitrogen content and root system parameters of plants were also significantly improved. GO + Rh-treated reduced the Na+/K+ ratio and the osmotic substances, while the activities of antioxidant enzymes SOD, POD, CAT and APX in GO + Rh-treated soybean plants increased significantly by 69.18%, 69%, 75.64% and 48.38% compared with the control plants. The REC, MDA and H2O2 content decreased significantly by 46.73%, 42.80% and 43.53%. In addition, GA3 content, among all related saline-alkali hormones, was increased by 100.20% compared with the Ctrl. The expression level of GmGBP1, a key gene for GA3 synthesis, at most increased 6.42 times compared to the Ctrl. The results further reveal that GO + Rh-treated obviously improves the yield traits of soybean plants, which confirms that GO + Rh-treated could be effective in enhancing soybean tolerance to saline-alkali stress. Our findings provide a new strategy for improving the saline-alkali tolerance of soybean, as well as a new perspective for exploiting and utilizing large-area saline-alkali soil.