The Quantitative and Qualitative Assessment of Auxin Hormone Production Ability of Same of the Iranian Soils Indigenous Rhizobial Strains

Now, it’s completely proved that we can find strains among many strains of each rhizobial group that can also do effective process in plant growth promoting as plant growth hormones production (IAA), in addition of their ability in N2 fixation. therefore, the aim of this research is to determinate the ability of IAA production of some of the indigenous rhizobial strains by two quantitative and qualitative methods. The results obtained from this study show that Rhizobial bacteria enable to produce auxin hormone (IAA). Moreover, this ability is not the same among various rhizobial species and among the strains belonging to each rhizobial species (p3), Rhizobium leguminosarum bv. Viciae (with HD/CD = 2.5 – 3) and Sinorhizobium meliloti (with HD/CD = 2 – 2.5) had the same production ability in both methods and also the strains of Mesorhizobium ciceri (with HD/CD= 1.5 – 2) and Bradyrhizobium spp (with HD/CD= 1 – 1.5) produced the small amount of IAA in both two methods.