Cluster P-6 consisted of 32 isolates. All grew at 40°C, were resistant

to heavy metals, and sensitive to streptomycin. They also grew at pH 4.5-9.5 and in medium supplemented with 1-4% Z-IETD-FMK concentration NaCl. These isolates had a wide range of water stress tolerance. Cluster P-7 consisted of 25 isolates. All grew in medium supplemented with 6% NaCl, at water stress level of -1.5 MPa and were resistant to heavy metals and antibiotics. Cluster P-8 consisted of 43 isolates that were resistant to heavy metals and to antibiotics. They grew at 32-40°C, 3-4% NaCl, and had good tolerance to water stress. Cluster P-9 consisted of four isolates, sensitive to Zn and resistant to antibiotics. They could grow at neutral-alkaline pH, were tolerant to water stress and to 5% NaCl. Cluster P-10 consisted of four isolates. All grew at 40°C, tolerant to salinity, water stress and this website were sensitive to heavy metals and streptomycin. Cluster P-11 consisted of nine isolates that grew

in medium supplemented with 3% NaCl, and had a wide range of tolerance to temperature, water stress and heavy metals. All isolates were sensitive to tetracycline. The phenotypic patterns observed in the cluster analysis clearly showed tolerance to the multiple environmental stresses which are common in marginal soils of arid and semi-arid regions. This kind of phenotypic diversity observed in the rhizobia populations could offer selective advantages in survival and adaptation to these harsh environments. Genotyping with rep-PCR resolved phenotypic diversity in S. meliloti and S. medicae Rep-PCR analysis of consensus sequences REP and ERIC, capable of amplifying repetitive and conservative elements diffused/dispersed in DNA, revealed high intraspecific

diversity among the 157 isolates and classified the isolates into 148 genotypes. Among the genotypes, only three genotypes were observed 2 times and one genotype was found 3 times and the remaining genotypes were detected only once. These identical genotypes were considered as clones and these clonal oxyclozanide isolates were found only in S. meliloti. Since, each genotype characterized by unique combination of rep-PCR profiles, these genotypes can be considered as different strains. The dendrogram was constructed based on the genotype profiles and provided more information on the specific variability of the strains (Figure 4). At 84% level, there were 13 definitely separated and delimited clusters of strains. Each cluster contained strains with a range of phenotypic diversity. Each cluster was formed by strains from different areas of collection and with different phenotypic traits, except the cluster G-4 (all the 4 strains of the cluster with the same phenotype). In other words, within the same location/region of collection, the strains architecture was phenotypically and genetically divergent.