Antagonistic Compounds Producing Plant Growth Promoting Rhizobacteria: A Tool for Management of Plant Disease

Agriculture is facing struggle to meet the various confront of reducing plant diseases for an increasing world population food security. Great quantities of synthetic fertilizers and pesticides are required for high productivity which can damage ecosystem structures and functions, including the soil microbial community which plays an important role in agriculture sustainability. Soil is an excellent niche of growth of much plant growth promoting rhizobacteria. PGPR are naturally occurring soil bacteria that aggressively colonize in plant roots and play a vital role in crop protection, growth promotion and in the improvement of soil health. Scientific researchers involve multidisciplinary approaches to understand adaptation of PGPR, effects on plant physiology and growth induced systemic resistance, biocontrol of plant pathogens and biofertilization. The primary mechanism of biocontrol by PGPR involves the production of antibiotics such as carboxylic acid, 2,4-diacetyl phloroglucinoloomycin,pyoluteorin,pyrrolnitrin,kanosamine,zwittemycin-A and pantocin. A cascade of endogenous signals such as sensor kinases, N-acyl homoserine lactones and sigma factors regulates the synthesis of antibiotics. Some of these antibiotics have broad spectrum against many plant pathogens like fungi, viruses and bacteria, affecting crop plants. These antibiotics also serve as determinants in triggering induced systemic resistance (ISR) in the plant system.