The effect of IAA-producing rhizobacteria native of Iran on bread wheat Roshan cultivar

At present, the use of plant growth-promoting bacteria has been considered as a suitable alternative to the use of chemical fertilizers to improve wheat growth. The objectives of this study was to identify the best and most effective rhizobacteria on wheat growth. First, Bacillus strains were isolated from wheat rhizosphere and their ability to produce IAA was assayed. Then, Triticum aestivum (Roshan) plants were treated in a completely randomized design by eight heighest IAA-producing bacterial strains at three different bacterial concentrations. By examining morphological traits, the best treatment was selected and the expression of genes involved in the auxin pathway was studied by RT-qPCR technique. Here, twenty Bacillus strains were isolated. The amount of IAA production varied among the strains (the minimum and maximum IAA production were 0 and 95.89 μg/ml, respectively). Twenty strains were isolated, eight strains with the highest levels of IAA production were selected for applying to the plants. Results of morphological traits demonstrated that strain C6 at concentration 1 (OD=1) had a significantly greater positive effect on Roshan plants. This strain was chosen for genes expression analysis. Analysis of expression of TaTAR2.1 and TaTAR2.4 genes showed that these genes have been influenced by strain C6 and they were significantly down-regulated as compared to the control.