Dual inoculation with rhizobia and arbuscular mycorrhizal fungus improves water stress tolerance and productivity in soybean

A glasshouse experiment was conducted to understand the influence of rhizobia, Bradyrhizobium liaoningense and an arbuscular mycorrhizal fungus, Ambispora leptoticha on growth and yield performance of soybean cultivars, MAUS 2 and MAUS 212 (drought susceptible) and DSR 12 (drought tolerant) under different levels of moisture stress conditions. Three different water levels [100%, 75% and 50% FC] with three microbial inocula (B. liaoningense, A. leptoticha and B. liaoningense + A. leptoticha) served as main treatments and the water level treatments were imposed 31-45 days after sowing. Various growth, physiological and microbial parameters were recorded besides analysing the samples for nutrients. The results showed that the plant growth parameters like biovolume index, total dry biomass, root volume and seed yield were significantly higher in dual inoculated plants in all the cultivars at all the moisture levels. There was an increase in mean seed weight by 88% and dry biomass by 58% in dual inoculated plants compared to uninoculated plants. Further physiological parameters and nutrients level improved significantly with dual inoculation under stress condition. However significant difference in recorded parameters was not observed in plants grown at 100% and 75% FC suggesting dual inoculation of B. liaoningense + A. leptoticha is beneficial when stress is severe in all the 3 cultivars. The microbial and nutrient parameters followed the same trend. Further of the two drought susceptible cultivars, MAUS 2 performed better compared to MAUS 212 in all the studied parameters under stress with dual inoculation. The results therefore signify the importance of rhizobia and mycorrhizal inoculation for imparting stress tolerance in soybean.