Rhizobium Enhanced Drought Stress Tolerance in Green Bean Plants Through Improving Physiological and Biochemical Biomarkers

D UE to global warming and climate change, drought is considered one of the major abiotic stressful conditions that causes numerous morphological, physiological, and biochemical changes that limit the plant growth and productivity. The enhancement of drought tolerance by the application of plant growth-promoting rhizobacteria has been progressively documented. Therefore, the present study was carried out to examine the potential role of Rhizobium leguminosarum biovar. Phaseoli in attenuating the adverse effects of water deficiency (80, and 60% of the estimated crop evapotranspiration) on growth, yield and quality and some biochemical and physiological parameters of green bean plants cv. Valentino. The experimental design was a randomized complete block design with three replications. The obtained results revealed that increasing water deficit severity resulted in decreases in plant growth characteristics, leaf nutrient content, SPAD readings, leaf relative water content (LRWC), leaf membrane stability index (LMSI) and yield components, as well as induced increments in proline content, catalase, peroxidase, and superoxide dismutase activities. However, application of Rhizobium leguminosarum considerably improved all growth and yield parameters and enhanced SPAD readings, RWC, MSI, proline content, and antioxidant enzyme activities. It could be concluded that Rhizobium leguminosarum inoculation could be used as a promising and sustainable strategy to cope with the adverse impacts of drought stress on green bean productivity in the forthcoming era of climate change.