Chapter 4 - Role and potential applications of plant growth-promoting rhizobacteria for sustainable agriculture

Abstract

The plant ecosystem is very prone to unfavorable environmental conditions. Plants are directly or indirectly affected by several biotic and abiotic factors facing everyday triggers causing the underdevelopment of plants leading disease. The agricultural soil and water system inhabit numerous natural microbial flora. Researchers are deeply working in the field of development of strategies to enhance plant growth promotion. One peculiar group of microbes called PGPR (Plant growth-promoting rhizobacteria) alleviates the effect of biotic and abiotic stress factors directly or indirectly. The plant growth-promoting bacteria have several properties such as iron chelating ability, phosphate solubilization, ACC deaminase enzyme production under saline stress, phytohormone production, and many more. This significant potential makes them a very unique microbial candidate as bioinoculants enhancing plant growth both in favorable and unfavorable conditions. They play a very important role in sustaining all different geochemical cycles in the environment such as the carbon cycle, phosphorus cycle, sulfur cycle, and nitrogen cycle. PGPR may present as normal and as an extremophilic microorganism. The current compilation and description inculcate various types of compatibility of PGPR with plants in different climatic conditions. Few PGPRs such as Bacillus, Klebsiella, Pseudomonas, Azobacter, Enterobacter, Serratia, Variovorax, and Azospirillum are commercialized in the agriculture system to make it more sustainable.