For comparison, soil bacterium Pseudomonas chlororaphis 63-28 (PC), which was isolated from the rhizosphere of canola grown in non-contaminated soil ( Paulitz et al., 2000), was also included. In addition to PC, we used wild type and two mutants of Pseudomonas fluorescens Pf-5 (PF) (PchA and PchC) to compare between siderophore-producing and non-producing mutants of the same bacteria. Mutant PchA is completely impaired in siderophore production whereas PchC is partially impaired