In a primary isolation process by using of soil paste and nitrogen free media, a total of 310 isolates were isolated from different soil samples located in East Azerbaijan, Gilan and Ardabil provinces. According to the phenotypic similarity and some characteristics related to the Azotobacteria, only 58 isolates were selected to assess their plant growth promoting (PGP) traits including production of siderophore and indole acetic acid (IAA), phosphate solubilization and potassium releasing under in vitro conditions. Moreover, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the 16S rDNA and nifH genes digested by MspI and HindIII was used to investigate its genetic diversity. The results revealed that almost 43% of the isolates were able to produce siderophore, and Pseudomonas 36A-2m isolate produced largest orange halo in CAS-agar plate. But the dissolution of phosphate was increased 14.5 times in the presence of tricalcium phosphate (TCP) than rock phosphate (RP). The maximum dissolution of TCP and RP obtained with Pseudomonas 23A-6 (196.83 mg/L) and Pseudomonas 34SP-III (30.60 mg/L) isolates, respectively. The released K from biotite was 1.75 fold more than muscovite, and the highest K release was observed by Citrobacter 44A-4s (17.52 and 11.06 mg/L for biotite and muscovite, respectively). Furthermore, the highest amount of IAA was obtained by Pseudomonas 23A-6 (15.17 mg/L) in the presence of 100 mg/L L-tryptophan. Although the goal was to isolate Azotobacteria, but molecular and biochemical identifcation revealed that the efficient isolates are belonging to the genera Azotobacter, Beijerinckia, Klebsiella, Stenotrophomonas, Pseudomonas, Rhizobium, Agrobacterium, Achromobacter and Sphingomonas. In this study, all of the Azotobacteria belonged to A. chroococcum species but they grouped in different branches in phylogenetic tree based on PCRRFLP analysis. The results suggest that, all but one A. chroococcum strain 35A-2 belong
