Ameliorating the drought stress tolerance of a susceptible soybean cultivar, MAUS 2 through dual inoculation with selected rhizobia and AM fungus

Abstract

Abstract Drought stress is currently the major and primary abiotic stress factor for crop loss throughout the world. Although drought stress reduces the yield significantly, crop species differ in their stress response with some tolerate the stress effect while others not. Soybean is one such crop species reported to be more sensitive to drought stress during flowering, pod set and pod filling stage leading to a significant yield loss. In several systems, it has been shown that the soil microbes ameliorate the stress effect and therefore, yield loss is minimized under stress conditions. Realizing the importance of useful soil microbes, a field experiment was conducted to study the effect of selected microbial inoculants namely, N-fixing rhizobial bacteria, Bradyrhizobium liaoningense and P-supplying arbuscular mycorrhizal fungus, Ambispora leptoticha on the growth and performance of a drought susceptible soybean cultivar, MAUS 2 under drought condition. Moisture stress was imposed at flowering and pod filling stage by withholding the irrigation and the results revealed that, dual inoculation with rhizobia, B. liaoningense + AM fungus, A. leptoticha has improved the physiological, biometrie and yield besides the nutrient uptake and utilization abilities of a drought susceptible and high yielding soybean cultivar, MAUS 2 under water stressed conditions. Under water stressed conditions, inoculation of plants with microbial consortia has increased number of pods and pod weight per plant by 19% and 34% respectively; while, the number of seeds and seed weight per plant increased by 17% and 32% over un-inoculated control plants. Further, the growth and yield data revealed that, the inoculated plants under stress were on par with the un-inoculated irrigated control plants suggesting that the dual inoculation of plants with useful microbes would alleviate the stress effects and thereby making the plants to grow normally. The study therefore, infers that, rhizobia and AM fungal inoculation seems to be necessary when soybean is cultivated under drought or water limiting condition.