Dynamic role of plant growth promoting rhizobacteria (PGPR) in agriculture

Plant Growth promoting rhizobacteria (PGPR) is a heterogeneous group of bacteria (eg- Pseudomonas, Azospirillum, Azotobacter, Klebsiella, Enterobacter, Arthrobacter, Burkholderia, Bacillus etc.) that are associated and colonized with root surface of plant. The rhizosphere of plant, contains different type of bacteria but only 2-5% of bacteria act as a PGPR (Antoun and Prevost, 2005). Bashan 1998; Gupta et al. 2000; Lucy et al. 2004 revealed that growth promoting ability of some rhizospheric bacteria is highly specific with plant species. In present scenario, PGPR plays an important tool for sustainable agriculture and trend for the future. The increasing demand for crop production with consequential reduction of synthetic fertilizers and pesticide use a big challenge. PGPR is a new alternative practice in Indian agriculture and it is an eco-friendly approach which can help by directly and indirectly mechanism to facilitating the growth and yield of the plant. The direct mechanisms likes nitrogen fixation, phosphate solublization, potassium solublization, siderophore production, phytoharmone production (i.e. IAA, Cytokinin, GA, Ethylene) etc. while indirect mechanisms likes Antibiotic production, Hydrolytic enzyme production, Induced systemic resistance (ISR), Exopolysaccharide production etc. The mechanisms of PGPR include regulating hormonal and nutritional balance, inducing resistance against plant pathogens and solubilizing nutrients for easy uptake by plants.