Endophytic Microbes and Their Role to Overcome Abiotic Stress in Crop Plants

In the process of growth and development, plants encounter both biotic (e.g., pests and pathogens) and abiotic environmental stresses (e.g., high and low temperature, high light, drought, heavy metals, heat, and salt). Due to the negative impact of various environmental stresses, the crop production decreases rapidly. Among stresses, abiotic stress is one of the principle causes of decreasing the average yield of major crops. Under stress condition in stress-tolerant plants, the extracellular stress signal is first perceived by the membrane receptors (G protein–coupled receptor, ion channel, receptor-like kinase, or histidine kinase), which results in the production of many secondary molecules such as Ca2+, inositol phosphate, reactive oxygen species, and abscisic acid. These ultimately lead to plant adaptation to stress tolerance. Mitogen-activated protein kinase (MAPK/MPK) cascades are highly conserved regulators of diverse cellular processes, such as differentiation, proliferation, growth, death, and stress responses. MAPK cascade plays a crucial role in various biotic and abiotic stress responses. Although plants itself have signaling mechanism to overcome stress situation, sometimes it has been seen that endophytic microbes reside within the host tissues and their metabolites directly or indirectly interact to induce host stress–tolerant genes. Overall, the stress response could be an outcome of coordinated action of many genes, which may cross-talk with each other. The symbiotic interactions between plant and endophyte may result in several outcomes as defined by fitness benefits by each of the partners. This chapter will focuses on the potential endophytic microbes that induce abiotic stress tolerance in crop plants.