Bradyrhizobia-mediated drought tolerance in soybean and mechanisms involved

Abstract

Among various legume crops grown across the world, soybean (Glycine max L. Merrill) is emerging as one of the fastest-growing oilseed crops in the world containing about 40% protein and 20% oil and is also being used as potential feed for animals. Drought stress being a major abiotic stress factor affects the soybean productivity adversely. Thus, to enhance the productivity of soybean, besides managing the nutrients, stress management is of utmost importance. There is enormous potential for opportunity of application of microbes especially bradyrhizobia either applied alone or co-inoculated with plant growth-promoting rhizobacteria (PGPR), and AM fungi can help in nutrient mobilization and confer tolerance to plants by alleviating adverse effects of stresses. Bradyrhizobia are mainly slow-growing, ubiquitous group of soil bacteria known as root symbiont; this is symbiotically associated with roots of soybean plants. In this chapter, we provided on how drought affects the soybean production worldwide and utilized specific bradyrhizobial strains to confer tolerance to soybean plants under drought stress and to understand the mechanisms imparting in the reduction of abiotic stress, e.g., GOGGAT MAPK, different polysaccharides, and other precursors involved in drought stress recovering mechanism. The enhancement of the soybean bradyrhizobial symbiosis participating in the drought tolerance particularly with climate smart bradyrhizobia having high osmotolerant traits, persisting longer in the field, and availability of such inoculants have also been discussed.