Isolation and Characterization of Local Isolates of Rhizobia in Nineveh Governorate/Iraq

In this study, thirty-six local isolates of rhizobial bacteria were isolated from root nodes of different leguminous plants collected from different areas in Nineveh Governorate/Iraq. The rhizobial colonies were purified and their agronomic and biochemical characteristics were studied. Results of this study showed that the local isolates had the ability to consume different sugars as a carbon source. Also, the antibiotic sensitivity test showed that only one isolate, <em>Rhizobium</em> <em>leguminosarum</em> bv. <em>phaseoli</em> AS12 was resistant to the antibiotic Azithromycin 15 µg/ml, and the isolate <em>Rhizobium</em> <em>leguminosarum</em> bv. <em>phaseoli</em> AS14 showed resistance to the antibiotic Gentamycin 10 µg/ml, and the rest of the isolates showed different rates of resistance and sensitivity for the rest of the antibiotics. The local isolates showed different NaCl tolerance levels up to 8.0 %, while no tolerance was observed for <em>Rhizobium</em> <em>leguminosarum </em>bv.<em> viciae</em> AS11 isolate at any of the studied concentrations. Results of heavy metal salt tolerance study showed that the isolates of <em>Ensifer meliloti</em> AS34 and <em>Rhizobium</em> <em>leguminosarum</em> bv. <em>viciae</em> AS36 were sensitive to ZnSo₄ at a concentration of 25 µg/ml, while the tolerability of the other isolates to the studied heavy salts differed at concentrations higher than 25 µg /ml. All the studied isolates showed a positive result in staining with Congo red and Aniline blue dyes. Maximum exopolysaccharide production was 494 mg/Li by <em>Rhizobium leguminosarum</em> bv. <em>viciae</em> AS35. Antimicrobial activity test showed maximum inhibition zone 17 mm by <em>Rhizobium leguminosarum</em> bv. <em>viciae</em> AS36 against <em>Proteus vulgaris.</em>