الملخص

Rhizobia represents one of the most important types of beneficial soil bacteria, as it contributes to fixing atmospheric nitrogen. In the present study, twenty four isolates of rhizobial bacteria were isolated from root nodules of six leguminous plants. These are Medicago sativa وTrigonella foenum-graecum, Cicer arietinum, Vicia faba, Lens culinaris and Lupinus spp. which planted in four regions of Ninevah province (wire farm house in the Education College / Mosul University , Ba'shiqah town and Sadaa & Bauazh) for the agricultural season 2010-2011. These isolates were put in six groups depending on diagnostic tests and type of plant host (alfalfa , fenugreek, chickpeas, bean , lentils and lupine)  from which the bacteria isolated from their  root nodules. These groups are RhM , RhT , RhC , RhF , RhL and RhLu respectively. RAPD – PCR technique with four random primers were used to draw the genetic Dendrogram in order to demonstrate the relationships among the species of rhizobial bacteria isolated from the root nodules of different host. The results revealed that there are genetic diversity among these species and also diversity still exist among the isolates of the same species but at low level. According to the results of diagnostic tests, RAPD – PCR technique and specificity of rhizobial bacteria to infect their hosts, we can relate the isolates in the suggested groups to their scientific names as follow: Sinorhzobium meliloti (RhM) , Sinorhzobium meliloti (RhT) , Rhizobium legumenosarum bv. cecir (RhC) , Rhizobium legumenosarum bv. vicia (RhF) , Rhizobium legumenosarum bv. lentil (RhL), Rhizobium lupini (RhLu).