Rhizobacteria: Legendary Soil Guards in Abiotic Stress Management

Abstract

All plants are continuously subjected to various types of biotic and abiotic stress factors from the time they have been planted in the field up to the time of harvesting, transport, storage, and consumption of the plant or plant-based products. These stresses result in the negative and deleterious effects on crop health and also cause enormous losses across the globe. To reduce the intensity of the losses produced by these stress factors, researchers all across the world are involved in inventing new management practices which may include traditional genetics methodology and various techniques of plant breeding. The use of microorganisms to mitigate both abiotic and biotic stress can provide an economical, eco-friendly solution to the problem of losses due to abiotic and biotic stresses. One such category of microorganisms is root-colonizing nonpathogenic bacteria like plant growth-promoting rhizobacteria (PGPR) which can increase the plant's resistance to biotic and abiotic stress factors. PGPR is the bacteria residing in the rhizosphere region and is involved in promoting plant growth and suppressing stress components. PGPR colonize the rhizosphere for nutrition which they acquire from plant root exudates. The mechanism by which plant growth-promoting rhizobacteria can accomplish the abovementioned task includes increment in plant growth by enrichment of soil nutrients through nitrogen fixation, solubilization of phosphates, production of metal ion chelators, and elevated production of plant growth-promoting hormones. The mechanism also focuses on elevated protection of the plants through influencing the levels of production of cellulases and beta-1,3-glucanases which result in the activation of the defense mechanism of plants against pests and pathogens. PGPR also contains useful variation for making plant tolerant to abiotic stress factors like temperature extremes, pH variations, salinity and drought, and heavy metal and pesticide pollution. Enrichment of plant rhizosphere with such potential stress-tolerating PGPR is expected to provide enhanced plant growth and high yield of plant products in stress-affected areas. This chapter summarizes the research related to PGPR and its benefits and also throws light on the involvement of PGPR in abiotic stress management.