Siderophore Efficacy of Fluorescent Pseudomonades Affecting Labeled Iron ( 59 Fe) Uptake by Wheat ( Triticum aestivum L.) Genotypes Differing in Fe Efficiency

Plant growth promoting rhizobacteria (PGPR) may enhance iron (Fe) availability by producing some organic products including siderophores. Accordingly, the potential of fluorescent pseudomonades (selected from among 201 isolated strains) to produce auxin (IAA) and siderophore (Sid) and their effects on 59Fe uptake by two different wheat genotypes (Tabasi and Yavarous) were determined. High siderophore producing super-strains of Pseudomonas putida, P. fluorescens, and P. aeruginosa were isolated from wheat rhizosphere and their potential for siderophore production was evaluated by the chrome azurol-S assay (CAS blue agar). P. putida, the most efficient strain, produced a siderophore complex with 76 % efficiency compared with the standard siderophore, siderophore desferrioxamine B (DFOB). Bacterial siderophores significantly and differently affected the uptake of labeled 59Fe by wheat genotypes (Tabasi the more efficient cultivar) indicating that there may be differences in the chemical structure of the siderophores. Siderophore effectiveness on Fe availability was in the following order: Sid-DFOB> Sid-putida> Sid-fluorescens> Sid-areuginosa.