The isolated PGPR differed significantly in ACC deaminase activity. In this study the highest ACC-deaminase activity was noted for S2,S9, S11, S12, which is related with the highest values for plantsbiomass. This effect was most pronounced for roots of rape (Fig. 2Band 4B). This positive correlation was also observed between thein vitro activity of this enzyme and the bacterial effect on plant rootelongation in the research conducted by other authors