Harnessing Plant Growth-Promoting Rhizobacteria: A Dual Approach as Biofertilizers and Biopesticides for Field and Vegetable Crop Production

Plant growth-promoting rhizobacteria (PGPR) are a widely known group of beneficial bacteria found in the rhizosphere. The PGPR can enhance plant growth and health via biological nitrogen fixation (BNF), production of plant hormones, solubilization of soil nutrients (P, K, Zn), and biocontrol of soil-borne pathogens. Consequently, some of the elite strains of the PGPR can be used as biofertilizers and biopesticides, representing an eco-friendly alternative to synthetic fertilizers and pesticides. The PGPR also contributes to improvement in crop productivity under fluctuable and/or adverse environmental conditions, featured by various biotic and abiotic stresses. This chapter summarizes the action mechanisms and the benefits of PGPR in terms of raising the quality and productivity of agricultural soils and products. Because PGPR are highly diverse, this review focuses on the bacteria most found in PGPR-based products intended for use in agricultural production, namely Azotobacter and Bacillus as extracellular PGPR (ePGPR) and Bradyrhizobium and Rhizobium as intracellular PGPR (iPGPR). This chapter also analyzes the beneficial effects of the bacterial genera on growth and health of several field and vegetable crops, as well as with a discussion on examining new approaches to the selection, formulation, and application of the desirable bacterial strains in the practical fields.