Based on phenotypic features, the isolates could be divided into three main groups at 92 % similarity. Nodulating isolates of those grouped in clusters II and III were grouped with reference strains ofMesorhizobium mediterraneumand M. ciceri, respectively. The three isolates of cluster I did not induce nodules on the host plant. Based on the analysis of the fingerprint patterns generated by enterobacterial repetitive intergenic consensus- and BOX-PCR, the strains were classi-fied into six clusters (A–F) at the 75 % similarity level. These six clusters could be further divided into several subgroups at the 85 % similarity level. The phylogenetic analysis based on 16S rRNAgene sequences showed that representative isolates were closely related toM. mediterraneum, M. ciceri,and Agrobacterium tumefaciens. Keywords16S rRNA.BOX-PCR.Chickpea.ERIC-PCR. Iran .Root-nodulating bacteria Introduction Chickpea (Cicer arietinumL.) is one of the major pulse crops throughout the world. It is cultivated on a large scale in arid and semi-arid environments and is an important food, feed, and fodder crop (Singh1997). Rhizobia are soil bacteria that are able to fix atmospheric nitrogen through their symbiotic association with legumes, and each rhizobial species has a different host range for plants with various metabolic capabilities (Wielbo et al.2010;Mar-garet et al.2011). Among the many parameters that have been postulated to affect the symbiotic efficiency of rhizobia in field environments, two key factors have been identified to be important in legume symbiosis: (1) nodule occupancy, which illustrates the competitiveness of a rhizobial strain among the bacterial community (Ben Romdhane et al. 2007b,2008)and(2)straineffectivenessfornitrogenfixation, which affects plant growth and yield (Ben Romdhane et al. 2008). Rhizobia are taxonomically, metabolically, and geneti-cally diverse and, according to classic rhizobia taxonomy, include the genera Allorhizobium, Ensifer/Sinorhizobium, Brad
