MODE OF ACTION OF PLANT GROWTH-PROMOTING RHIZOBACTERIA AND THEIR POTENTIAL USE AS BIOLOGICAL-CONTROL AGENT

Plant growth-promoting rhizobacteria, known as PGPR, stimulate directl y plant growth by increasing plant nutrients uptake, by inducing and p roducing plant growth regulators and by activating the induced resista nce mechanisms in plants. PGPR stimulate indirectly plant growth by th eir antagonistic effect on detrimental microflora, by transforming tox ic metabolites and by stimulating the nodulation of leguminous plants by rhizobia. The PGPR antagonistic effects is due to the production of antibiotics and to the competition for nutrients with plant pathogens . The establishment of the PGPR-plant association is essential for the expression of beneficial effects to plants. Using PGPR marked with bi oluminescence genes allows to observe the root colonization process. F ollowing the appearance of seed exudates, the bacterial inoculum repro duces and the bacteria are passively carried away from the seed zone w ith the developing root. Subsequently, PGPR continue to reproduce foll owing stimuli from the root exudates and remain on the roots. Many com panies are developing inoculants containing PGPR, in order to reduce t he use of synthesized pesticides in agriculture.