Modulating Nutrition, Physiology and Production of Maize Through Rhizobium phaseoli and Mesorhizobium ciceri Inoculation under Drought Stress Conditions

Water scarcity is a potential effector restraining crop yield and economic returns to the farmers. This situation may be rescued by inoculating drought tolerant rhizobia owing to their plant growth promotion attributes and high root colonization efficiency. A pot experiment was conducted in sandy clay loam to assess the potential of four drought tolerant rhizobial strains Rhizobium phaseoli-RS-1, R. phaseoli-RS-3, Mesorhizobium ciceri-RS-8 and M. ciceri-RS-12 for ameliorating drought impact in maize. The stress was applied at five leave (vegetative) and silking (reproductive) stages. Rhizobial strain RS-8 significantly (p=0.05) decreased electrolyte leakage and increased root/shoot dry biomass, 100-grain weight and ultimately the grain yield in normal and drought condition compared to respective uninoculated control. Differential response of rhizobial inoculation was observed on physiological characters and plant nutrient uptake under normal and drought condition, however, RS-1 and RS-8 showed more promising for improving chlorophyll contents, photosynthetic/transpiration rate, intrinsic water use efficiency, stomatal/mesophyll conductance, relative water contents and nutrient uptake in maize subjected to normal and drought conditions. Moreover, root colonization capability of RS-1 (5.52×10 CFU cm root) and RS-8 (5.89×10 CFU cm root) was higher than control (2.3×10 7 1 7 1 4 CFU cm root) and other strains under normal irrigation. Similarly, higher root colonization efficiency of RS-1 1 and RS-8 was observed under drought stress which seems to improve plant yield by modulating physiological characters and nutrient uptake in stress conditions. Thus, the results are encouraging in the utilization of rhizobial strains (RS-1, RS-8) as biofertilizer for sustainable production of maize under water deficit conditions.