Effect of superior indole-3-acetic acid producing Rhizobia and the combination with Ag and L-tryptophan on wheat growth indices under in vitro conditions

An in vitro study was conducted to determine the effects of the superior indole-3-acetic acid (IAA) producing Rhizobia and treatments of Ag and L-tryptophan (Trp) on wheat growth indices. Nine strains with different ability of IAA production (belonging to genus Rhizobium leguminosarum var. phaseoli and Rhizobium leguminosarum var. viciae, Sinorhizobium meliloti) and a non-inoculated control; two levels of L-Trp (0 and 100 mg/l) and two levels of Ag (0 and 10 mu M) were used. Plants were grown for 14 days and plant root dry weight, root length, stem length and stem dry weight were determined. Plants inoculated with the rhizobia and their combination with Ag and L-tryptophan (Trp) gave the highest root dry weight, root length, stem length and stem dry weight compared to non-inoculated control plants. The experiment indicated that rhizobia could be used as bioenhancer and biofertilizer for wheat production and also usage of both Ag and Trp treatments simultaneously resulted in a significant increase on measured parameters in comparison with the separate application of Ag and Trp and also in comparison with the blank. Therefore, the Rhizobia can increase plant root growth, by producing IAA what might lead to uptake of more nutrients from the root environment.