Molecular mechanisms in plant growth promoting bacteria (PGPR) to resist environmental stress in plants

Abiotic stresses have negative impacts on the crop production, by altering plants mechanisms. Drought (water deficit stress), salinity, etc can be enlisted in the abiotic stresses affecting crop productivity. Sustainable agriculture maintains and improves the quality of resources of environment, satisfying changing human requirements, where use of plant growth promoting rhizobacteria (PGPR) can be approached. Bacteria residing in rhizosphere region are the rhizobacteria, which are usually attached to the soil particles, in the vicinity of roots because of abundant food sources around them. PGPR efficiently secrete miscellaneous chemical regulators in vicinity of rhizosphere by colonizing plant roots thereby promoting plant growth. Recently, there is an increasing number of researchers in investigating various aspects to maximize the efficiency of PGPR utilization in reducing inputs of chemical fertilizer in crop production. This chapter elucidate the effects of drought stress and salinity stress on crop plants, and influence of PGPR under drought and salinity stress along with their molecular mechanisms, osmotic balance, modification of phytohormonal activity, ion homeostasis was deliberated extensively.