The role of microbial activity on iron uptake of wheat genotypes different in fe-efficiency

Soils in many agricultural areas have high pH, resulting in low availability of Fe. Wheat grown on such soils suffers from most micronutrient deficiencies, in particular Fe deficiency. The objective of this investigation was to determine the potentials of indigenous fluorescent Pseudomondas for siderophore production and their effects on 59Fe acquisition. For this purpose, some strains of Pseudomonas putida, Pseudomonas fluorescens, and Pseudomonas aeruginosa were isolated from different locations representing rhizosphere of wheat. The potentials of these strains for siderophore production were evaluated by chrome azorel-S assay (CAS blue agar) through color change. High siderophore producing Super-strains were selected for extraction of siderophores. These isolates were grown in SSM (standard succinate medium) for 72 hr at 28 C. Bacterial cell were removed by centrifugation (10000 g for 20 min) and the supernatant was filtered through filter membrane (0.22 ) and used as crowd siderophore. Evaluation of Fe uptake and translocation were carried out with complexes of bacterial siderophores and 59Fe compared with standard sierophore Desferrioxamine (DFOB) in randomized complete block design with three replications. This experiment was conducted on two wheat genotypes different in Fe-efficiency at hydroponic condition. The results showed that among the three most effective siderophores producing strains considered, the P. putida produced a sidrophore complex that showed efficiencies of 76 %, compared with the standard siderophore (DFOB) in the uptake of Fe and was statistically in the same group as the control. The effect of bacterial siderophores in the uptake of labeled 59Fe by wheat became significant, indicating that the chemical structure of the siderophores from different strains were different. The effects of wheat genotype in 59Fe activity of shoots was also significant, where the efficient Tabasi genotype contained 46 % more Fe in shoots than the inefficient Yavarous genotype. It was concluded that the siderophore complex from P. putida was the most effective in translocating Fe to shoots, particularly in efficient Tabasi genotype. Siderophore effectiveness in Fe availability decreased in the order; Sid-DFOB> Sid-putida>Sid-fluorescens> Sid-areuginosa

The effect of PGPR inoculation on the growth of wheat

Many agricultural soils of Iran have high pH, resulting in low availability of Fe and Zn. The potentials of nonsymbiotic plant growth-promoting rhizbacteria (PGPR) for stimulating plant growth have been extensively used during recent decades. This experiment was carried out in growth chamber to evaluate the effects of siderophoreproducing Pseudomonads on the growth as well as Fe and Zn uptake of wheat. A randomized complete block design experiments was conducted using with Alborz genotype (an efficient phytosiderophore-producing bread wheat) treated with either 7NSK2 strain as a siderophore positive (sid+) or with MPFM1 mutant strain of the same isolate as a siderophore negative (sid-) treatments with three replications. The potentials of these strains for auxin production and phosphate solubilizing activity were evaluated by standard methods. The results showed that inoculation with sid+ strain increased dry matter production in shoots as compared with the control (sterile condition) or with sid - strain. Likewise, the concentration of chlorophyll a in leaves of sid+ and sid - treatments were 1.27 and 0.41 g mg-1 of fresh weight, respectively, and the concentration of chlorophyll b were measured to be 1.09 and 0.35 g mg-1 of fresh weight, respectively, indicating significantly more chlorophyll formation due to inoculation with sid+ as compared with sid -. The uptake of Fe by roots and its rate of translocation to the shoots were greater for the sid+ treated plants as compared with the sid - treated ones, indicating that siderophores increased the rate of Fe uptake by wheat. The effect of microbial inoculation on shoot Zn was not significant, but increased the concentration of Zn on roots compared with control. The results suggested that the siderophores of Pseudomonads may involve on increasing bioavailability of iron