Benefits of Plant Growth-Promoting Rhizobacteria and Rhizobia in Agriculture

Abstract

The rhizosphere is the volume of soil under the influence of plants roots, where very important and intensive microbe–plant interactions take place. These interactions can both significantly influence plant growth and crop yields and have biotechnological applications. The rhizosphere harbors a diverse community of microorganisms that interact and compete with each other and with the plant root. The activity of some of the members of this community affects the growth and the physiology of the others, as well as the physical and chemical properties of the soil. Among all these interactions, those resulting in symbiotic and non-symbiotic nitrogen fixation are considerably important. In recent years, the use of bacteria (rhizobacteria) to promote plant growth has increased in several regions of the world and has acquired relevant importance in developing countries that are the producers of raw materials for food. Rhizobacteria can affect plant growth by producing and releasing secondary metabolites, which either decrease or prevent the deleterious effects of phytopathogenic organisms in the rhizosphere, and/or by facilitating the availability and uptake of certain nutrients from the root environment. Significant increases in the growth and yield of agriculturally important crops in response to inoculation with rhizobacteria have been reported. This practical application of plant growth-promoting rhizobacteria is the main focus of this chapter.