Phenotypic properties (growth characteristics, utilization of carbon and nitrogen sources, and intrinsic antibiotic resistance) of 53 Rhizobium strains isolated from root nodules of the temperate-zone legumes Astragalus spp. (29 strains), Oxytropis campanuhta (7 strains), Hedysarum alpinum (7 strains), Ononis awensis (3 strains), Glycyrrhiza spp. (4 strains), and Coronilh varia (3 strains) were compared with those of other Rhizobium, Bradyrhizobium, and Agrobacterium strains. The final matrix, containing 83 strains and 56 nonsymbiotic features, was used for computer cluster analysis. The dendrogram showed that the new strains of temperate-zone rhizobia formed a cluster separate from both Rhizobium and Bradyrhizobium spp. Two large groups of temperate-zone rhizobia were revealed. Group 1 included rhizobial strains originating from different geographical regions with a temperate climate, while group 2 included strains from the same geographical origin, South Siberia. The 'strains of recognized Rhizobium species were clustered, in general, with each other as expected from phylogenetic relatedness.Root nodule bacteria of the genera Rhizobium and Bradyrhizobium are a common microflora of temperate soils. These bacteria may interact with the roots of leguminous plants, inducing the formation of nodules in which the fixation of atmospheric nitrogen occurs. These bacteria are commonly used in agriculture for improvement of plant growth. The specificity of the interaction between rhizobia and legumes depends on many factors coded for by the host cultivar and bacterial genomes;. The main properties of a bacterial isolate can be described by its taxonomical position in relation to other strains. There are several Rhizobium species recognized at this time (10, 1.3, 24), and knowledge of rhizobial evolution and phylogeny obtained in recent studies allows the proposal of new rhizobial taxa (3,16,25). However, the current systematic description of the genus Rhizobium does not include many of the root nodule isolates from legumes of tropical (22, 37), arctic (21), and temperate (5, 12, 17) regions.The host plant specificities and phage sensitivities of Rhizobium strains from temperate-zone legume root nodules formed on Astragalus, Hedysamm, Glycywhiza, and Ononis plants were recently described (17). It was shown that these strains constitute a cross-inoculation group related to Rhizobium loti. The aim of the present work was to determine the cultural properties of these strains and to compare these properties with those of other Rhizobium species. MATERIALS AND METHODSBacterial strains. Bacterial strains used in this work are listed in Table 1. Bacteria were maintained on yeast extractmannitol (YEM) (29) agar slants at 4°C.Growth characteristics. The time necessary for full colony development on YEM agar (estimated here as a colony diameter of 2 mm) was determined. Bacterial growth on meat-peptone agar and reactions with litmus milk were determined as described earlier (11). The ability of strains to grow in the presence of 0,1...