Chapter 18 - Metabolic and genomic traits of PGPR in salinity stress

Abstract

Soil salinity is a major abiotic factor which adversely affects the crop growth and productivity worldwide. Approximately 5.2 billion hectare agriculture land is affected by erosion, salinity, and soil degradation. Salinity stress has been significantly affecting the fertile lands, and therefore possesses a huge impact on the agriculture and economy of a country. Salt stress has severe effects on the growth and development of plants as well as reducing its yield. Plants are inherently equipped with stress tolerance ability to respond to the specific type of stress. Plants retained specific mechanisms for salt stress mitigation, such as hormonal stimulation, ion exchange, antioxidant enzymes, and activation of signaling cascades on their metabolic and genetic frontiers that soothe the stressed condition. Particular attention is paid toward the application of plant growth–promoting bacteria (PGPB) in agriculture system for producing salt stress–tolerant crops and a fundamental understanding toward the mechanisms of beneficial plant–microbe interaction in the presence of salt. Plant growth–promoting rhizobacteria (PGPR) are able to provide cross-protection against stress factors and facilitate the growth of their plant symbionts in many ways. PGPB also have a specialized mechanism that plays a key role for salt stress tolerance and plant growth promotion. These bacteria trigger plants to produce different plant growth hormones such as auxin, cytokinin, and gibberellin as well as volatile organic compounds. The beneficial effects of PGPR involve boosting key physiological processes, including water and nutrient uptake, photosynthesis, and source–sink relationships that promote growth and development and increase the agriculture productivity; the only possible environment-friendly approach is to improve the agricultural land already in use. The application of PGPR inoculants is a promising measure to combat salinity in agricultural fields, thereby increasing global food production.