Agricultural Sciences: Techniques and Innovations Vol. 12

Plant growth-promoting rhizobacteria (PGPR) are beneficial root-associated bacteria that can enhance plant performance through direct and indirect mechanisms. Their functions include biological nitrogen fixation, mobilization of poorly available nutrients, phytohormone modulation, siderophore-mediated iron acquisition, antimicrobial activity, induced systemic resistance and stress mitigation. Despite extensive evidence under controlled conditions, field performance remains inconsistent because inoculant efficacy depends on strain–plant compatibility, root colonization, soil and climatic conditions, interactions with resident microbiota, formulation stability, storage and application practices. This narrative review integrates established mechanisms of PGPR action with evidence on formulation, field performance, commercialization and deployment. Particular attention is given to carrier-based and liquid formulations, encapsulation and emerging nano-enabled delivery systems, while distinguishing demonstrated benefits from technologies that remain primarily experimental. The review also examines biosafety, regulatory and adoption constraints and identifies priorities for developing PGPR products with reproducible field efficacy and practical value in sustainable agriculture.