Plant growth promoting Rhizobacteria: An overview

Numerous species of soil bacteria which flourish in the rhizosphere of plants, but which may grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria).Of the microorganisms that parasitize on nematodes and reduce nematode populations by antagonistic behaviour, bacteria hold an important position where some of them have shown great potential as biocontrol agents. Bacteria destroy nematodes continuously in virtually all soils because of their constant association with nematodes in the rhizosphere. Although a large number of bacteria have shown antagonistic effects against nematodes but the most important genera include Rhizobium (R. leguminosorum), Bradyrhizobium japonicum, Mesorhizobium sp., Azorhizobium sp., Pseudomonas (P. fluorescens and P. aeruginosa) and Bacillus (B. subtilis). Application of some of these bacteria has accorded promosing results. There are several reports in the literature indicating that PGPR could be proved a boon in sustainable agriculture. Their beneficial events could be biological control of diseases and pests, plant growth promotion, increase in crop yields and quality improvement that can take place simultaneously and sequentially. There is an urgent need to develop some easy to manage technologies for formulation and mass production of bacteria at a commercial scale for field application.