Bioprotection of Soybean Plants from Drought Stress by Application of Bacterial and Fungal Endophytes

Soybean [Glycine max (L.) Merrill] is counted as the most important legume oilseed crop worldwide known for its high protein (35–40%) and oil (18–20%) content. Global climatic changes with persistent droughts are a major challenge and limiting factor for sustaining the yields of soybean. Several adaptations and mitigation strategies are required to cope with drought stress. Conventional breeding approaches employed for evolving drought-tolerant lines although is a viable solution requires more time and is long-term approach. As an alternate strategy, the use of microbial endophytes (bacterial and fungal) could play a significant role in the alleviation of drought stress and confer tolerance to plants. These beneficial microorganisms colonize the rhizosphere/phyllosphere of plants and impart drought tolerance by producing exopolysaccharides (EPS), phytohormones, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and volatile compounds and inducing accumulation of osmolytes and antioxidants, upregulation or downregulation of stress-responsive genes, and alteration in root morphology thereby making plants tolerant to cope during drought stress. The term induced systemic tolerance (IST) was also discussed on how physical and chemical changes induced by endophyte in plants which result in enhanced tolerance to drought stresses. In the present chapter, we also elaborated the role of bacterial and fungal endophytes and underlying mechanisms involved in helping soybean plants to cope with drought stress.