Plant Growth-Promoting Rhizobacteria (PGPR): Sustainable Agriculture to Rescue Vegetation from Biotic Stress – A Review

Abstract

Modern agriculture faces increasing pressure from biotic stresses such as fungal, bacterial and viral diseases, nematodes and insect pests, which together cause substantial yield losses and threaten global food security. Over-reliance on synthetic pesticides has led to environmental pollution, resistance development in pathogens and pests, and negative impacts on non-target organisms and human health. Plant growth-promoting rhizobacteria (PGPR) have emerged as a promising, eco-friendly alternative or complement to chemical inputs. PGPR are root-associated bacteria that enhance plant growth and health through multiple direct and indirect mechanisms. Direct mechanisms include biological nitrogen fixation, solubilization of phosphorus and other nutrients, production of phytohormones, siderophores, volatile organic compounds and ACC deaminase. Indirect mechanisms involve antibiosis, competition for nutrients and niches, production of cell wall–degrading enzymes, and activation of plant defense responses such as induced systemic resistance (ISR) and induced systemic tolerance (IST). Recent studies demonstrate that PGPR can effectively mitigate biotic stress caused by fungi, bacteria, viruses, nematodes and insect herbivores in diverse crops, while also improving resilience to abiotic stress, thereby contributing to sustainable intensification of agriculture.

This review summarizes the diversity and mechanisms of PGPR, with special emphasis on their role in managing biotic stress and enhancing plant immunity. Formulation technologies, modes of application and integration of PGPR into sustainable crop protection strategies are discussed. Finally, the review highlights current challenges, regulatory and commercialization issues, and future perspectives for large-scale adoption of PGPR-based bioproducts in agriculture.