Biosynthesis of Antibiotics by PGPR and Their Roles in Biocontrol of Plant Diseases

Abstract

Plant growth-promoting rhizobacteria (PGPR) plays an essential role when it comes to protection of crop, promoting growth, and improvement on soil health status. There are some prevalent PGPR strains such as Pseudomonas, Bacillus, Azospirillum, Rhizobium, and Serratia species. The key mechanism of biocontrol by PGPR is the involvement of antibiotics production such as phenazine-1-carboxylic acid, 2,4-diacetyl phloroglucinol, oomycin, pyoluteorin, pyrrolnitrin, kanosamine, zwittermicin-A, and pantocin. The cascade of endogenous signals such as sensor kinases, N-acyl homoserine lactones, and sigma factors regulates the synthesis of antibiotics. The genes which are responsible for the synthesis of antibiotics are greatly conserved. The antibiotics of this PGPR belong to polyketides, heterocyclic nitrogenous compounds, and lipopeptides which have broad-spectrum action against several plant pathogens, affecting crop plants. Though antibiotics play a vibrant role in disease management, their role in biocontrol is questioned due to limitations of antibiotic production under natural environmental conditions. In addition to direct antipathogenic action, they also serve as determinants in prompting induced systemic resistance in the plant system.