Plant Growth Promoting Rhizobacteria (PGPR): A Sustainable Agriculture to Rescue the Vegetation from the Effect of Biotic Stress: a Review

Many biotic agents such as bacteria, viruses, nematodes, arachnids, and weeds encounter the plants. These entities induce biotic stress in their hosts with the aid of disrupting normal metabolism, resulting in limited plant growth and causing plant mortality. As Arbuscular Mycorrhizal Fungi (AMF), plant-associated microbes can regulate physiological and molecular responses to cope with pathogenic biotic stress via enhanced antioxidant defense systems and mitigate oxidative stress. Several microbes can benefit plant growth and perform a similar role as pesticides and chemical fertilizers, acting as a biofertilizer and biopesticide. Plant growth-promoting rhizobacteria (PGPR) can expressively heighten plant growth and represent a mutually helpful plant-microbe interaction by facilitating the surroundings' nutrient uptake. The rhizobacteria such as Bacillus sp. can form spores that help them survive for a long period under harsh environmental conditions. PGPR can augment plant growth by introducing induced systemic resistance, antibiosis, and competitive omission and resisting the plants against biotic agents. Bacillus subtilis exhibits both a direct and indirect biocontrol mechanism to suppress disease and provide resistivity towards pathogenic pests caused by pathogens. These mechanisms assist the plant in its protection from the pathogenic onset. The present review discusses Plant Growth-Promoting Rhizobacteria's biocontrol potential and its role as a root colonizer. The associated biocontrol mechanisms of these PGPR to increase crop productivity under biotic stress conditions.