Synergistic Practicing of Rhizobacteria and Silicon Improve Salt Tolerance: Implications from Boosted Oxidative Metabolism, Nutrient Uptake, Growth and Grain Yield in Mung Bean

Plant growth promoting rhizobacteria (PGPR) and silicon (Si) are known for alleviating abiotic stresses in crop plants. In this study, Bacillus drentensis and Enterobacter cloacae strains of PGPR and foliar application of Si were tested for regulating the antioxidant metabolism and nutrient uptake on grain yield of mung bean under irrigation of saline water (3.12 and 7.81 dS m−1). Bacterial inoculation and supplemental Si (1 and 2 kg ha−1) reduced salinity-induced oxidative stress in mung bean leaves. The improved salt stress tolerance was achieved by enhancing the activities of catalase (45%), peroxidase (43%) and ascorbate peroxidase (48%), while decreasing malondialdehyde levels (57%). Enhanced nutrient uptake of magnesium 1.85 mg g−1, iron 7 mg kg−1, zinc 49.66 mg kg−1 and copper 12.92 mg kg−1 in mung bean seeds was observed with foliar application of Si and PGPR inoculation. Biomass (7.75 t ha−1), number of pods per plant (16.02) and 1000 seed weight (60.95 g) of plants treated with 2 kg Si ha−1 and B. drentensis clearly outperformed treatments with Si or PGPR alone. In conclusion, application of Si and PGPR enhances mung bean productivity under saline conditions, thereby helping exploitation of agriculture in low productive areas.