Effect of Some Environmental Factors and Antibiotics on the Growth of Different Species of Rhizobium

Six native rhizobial isolates from various cultural zones in Ninavah-Governate, Iraq, were used in this investigation. The following rhizobial strains were isolated from leguminous plant root nodules: Rhododendron japonicum SM29 from Glycin max L., Rhizobium leguminosarum bv. trifolii SM35 from Trifolium alexanrinum L., Rhizobium leguminosarum bv. viciae SM10 from Vicia faba L., Ensifer ferdii bv. Fredii SM13 from Vigna unguiclata L., Ensifer meliloti SM28 from Medicago sativa L., and Rhizobium leguminosarum bv. phaseoli SM42 from Phaseolus vulgaris L. Rhizobial bacteria were identified by the spherical, clear colonies seen after cultural investigation. Methyl red and Voges-Proskuar biochemical tests yielded negative results, but urease, catalase, indole, starch, Congo red, citrate, and motility tests yielded positive results. A high tolerance was found by the KNO3 tolerance test.