Effects of Microbial Siderophores Produced by Native Azotobacter chroococcum Strains on icronutrients Uptake by Wheat Plant

In this study, 14 strains of A. chroococcum isolated from wheat grown fields around the city of Tabriz, in northwest of Iran, were assayed for siderophore production using chrome azurol-S agar (CAS-agar) method under in-vitro conditions. Results showed that some strains had relatively higher ability in siderophore production. In a pot culture experiment with sterile soil, wheat plants (Triticum aestivum L.CV. Falat) were inoculated with 14 bacterial strains. Positive control received nitrogen fertilizer without bacterial inoculation and negative control was left un-inoculated and without N- fertilizer. Totally, 16 treatments with four replications were arranged in completely randomized design. Concentartions and contents of Fe, Cu, Zn and Mn in shoot and root as well as translocations of these elements from root to the shoot were determined at the harvest time. Results showed that the inoculation with Azotobacter had significant effects on concentrations and contents of Fe, Zn and Cu in shoot and root. Translocations of Fe, Zn and Cu from root to the shoot were markedly increased in bacterial treatments compared to the positive and negative controls. Mn concentration and content as well as its translocation from root to the shoot were not significantly affected. In-vitro assessment of siderophore production revealed that the higher siderophore production in bacterial stains was in accordance with higher Fe in plant tissue and its translocation as well.