Abstract

Plant growth-promoting rhizobacteria (PGPR), are beneficial bacteria that colonize plant roots and enhance plant growth through a variety of mechanisms that include improvement of plant nutrition, production and regulation of phytohormones, and suppression of disease causing organisms. Whereas members of the bacterial genera Azospirillum and Rhizobium are well-studied examples for plant growth promotion, Bacillus, Pseudomonas, Serratia and Stenotrophomonas are model organisms to demonstrate influence on plant health. Based on their ability to stimulate plant growth, it is possible to develop microbial inoculants for use in agricultural biotechnology. Depending on their mode of action and effects, these products can be used as biofertilizers and biocontrol agents. This application can help to minimize dependence on chemical fertilizers which have adverse effects on the environment. Despite their different mechanisms of action, their use has not been developed to its full potential due to inconsistencies in their performance, and their commercialization has been limited to a few developed countries. The purpose of this review is to give an overview on different mechanisms of action involved in plant-growth promotion.

Key words: Rhizobacteria, mechanisms of actions, plant growth-promoting rhizobacteria (PGPR).