Integrative Application of Soil P-Solubilizing Bacteria and Foliar Nano P Improves Phaseolus vulgaris Plant Performance and Antioxidative Defense System Components under Calcareous Soil Conditions

Potential influences of soil inoculation using phosphate-solubilizing bacteria (PSB) in integration with or without foliar spraying using mono-ammonium phosphate (MAP) or nano-phosphorus (NP) on performances, physio-biochemical attributes, and antioxidative defense system components in Phaseolus vulgaris plants were identified. A greenhouse preliminary and main pot experiments were conducted in calcareous soil (22% CaCO3) during fall and summer seasons of 2017/2018 and 2018/2019 in a completely randomized design. Preliminary experiments showed that the four concentrations: 1.0, 0.1, 0.5, and 0.05 g L-1 were the best for MAP, NP, and MAP when applied in integration with PSB, and NP when applied in integration with PSB, respectively, yielding the best results for plant growth and yield, total chlorophylls and P contents, and PSII efficiency (Fv/Fm). Therefore, these concentrations were selected for the main study. In main experiments, soil PSB or foliar MAP or NP resulted in significant increases in plant growth and yields, photosynthetic efficiency, gas exchange, relative water content, membrane stability index, ascorbate (AsA) and glutathione (GSH) contents and their redox states, contents of P, soluble sugars, glycine betaine, and activities of proline dehydrogenase (ProDH), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) compared to controls. In contrast, oxidative stress biomarkers (electrolyte leakage, lipid peroxidation, superoxide, and hydrogen peroxide), contents of proline and P5C, and activities of P5SC and phosphatase were significantly reduced. However, integrative PSB+MAP or PSB+NP treatment further improved all abovementioned parameters in plants. Integrative PSB+NP was the best treatment, awarding best improvements in all investigated parameters. Therefore, it can be recommended for cultivation and sustainability of Phaseolus vulgaris crop in calcareous soils.