Plant Growth-Promoting Rhizobacteria: Benign and Useful Substitute for Mitigation of Biotic and Abiotic Stresses

Abstract

An incessant increase in global population along with a continuous augmentation in abiotic stress conditions, such as temperature, pH, salinity, etc., and limitation of natural resources has posed a serious threat to developing nations in terms of food security and enhanced nutritional value of the yield. Substantial crop losses in both qualitative and quantitative aspects due to the several prevalent phytopathogens are adding severity to the existing trouble. Confrontation with this ongoing problem initially led to the application of chemical fertilizers. However, hazardous aftereffects of the chemical fertilizers on the ecosystem have instigated a demand for a promising eco-friendly substitute that deals with both biotic and abiotic stresses. Rhizospheric microorganisms can be utilized as an effective alternative because they reside in soil and have the intrinsic property of upholding balanced ecosystem. These plant growth-promoting rhizobacteria (PGPRs) enhance plant growth even in poor and stressed environmental conditions by the formation of beneficial associations with the host through biological nitrogen fixation, phosphate solubilization, siderophore and hormone production, etc. They can also trigger host defense mechanism through induced systemic resistance (ISR). These PGPRs are also helpful for phytoremediation by various processes such as direct absorption, accumulation, etc. PGPRs are utilized in the fields of phytostimulation, biofertilization, and biocontrol activities. In the current chapter, we would aim to uphold the mechanisms opted by PGPR for effective plant growth promotion and defense under various abiotic as well as biotic stress conditions. In this context, we would also aim to delve in detail about the host-PGPR cross talk during the onset of stress conditions.