Role of Plant Growth-Promoting Rhizobacteria in Combating Abiotic and Biotic Stresses in Plants

Global climate change accelerates the coincidence of a variety of abiotic stresses, viz., salinity, drought, flooding, high and low temperature, and biotic stresses, viz. phytopathogens which degrade agricultural productivity. In such circumstances, plant growth-promoting rhizobacteria (PGPR) are eco-friendly and sustainable candidates to combat these stresses. Several PGPR with the ability to support plant growth under various stressed conditions have been commercialized. The current chapter is mainly restricted to beneficial effects of PGPR on plant growth and development under environmental and biotic stresses. It begins with the description of various abiotic and biotic stress factors affecting plant growth and their tolerance achieved by both physiological and molecular mechanisms of adaptation. The use of PGPR helps ameliorate these stresses in rhizosphere by using several mechanisms and has beneficial effects on plant growth after efficiently colonizing the root surface. Plant growth stimulation through PGPR is the net result of multiple mechanisms of action that may be activated simultaneously. Such bacteria are more likely to be used for stress tolerance to fulfill the need for food production under extreme environmental conditions. The bacterial inoculants also enhance nutrient uptake and crop growth. They are also involved in biocontrol so they may be good supplements to chemical fertilizers and agrochemicals. This chapter discusses the potential and key mechanisms used by PGPR under stress conditions for sustainable agricultural productivity followed by their prospects.