The PGPR include free-living soil bacteria that occur in the root zone and endophytic bacteria,colonizing the root cells. The largest group of PGPR bacteria are Pseudomonas, Bacillus, Enterobacter, and Erwinia. Indoleacetic acid(IAA) that is produced by the bacteria may enhance the effects of plant auxin and can directly affect root growth by stimulating celldivision and elongation of the plant (Kalitkiewicz and K˛epczy´nska,2008).