NUMERICAL TAXONOMY AND DNA-DNA HYBRIDIZATION OF RHIZOBIAL STRAINS ISOLATED FROM THE LOESS PLATEAU OF CHINA
黄土高原根瘤菌数值分类及DNA-DNA杂交

Thirty-five new rhizobial isolates from the loess plateau of China and 32known strains representing all known species of Rhizobium and Bradyrhizobium werecharacterized by numerical taxonomy and DNA analysis. New strains were mainlyisolated from the nodules of genera Amorpha, Camilla, Amblytropis, Caragana,Amphicarpaea, Glycyrrhiza, and Sophora. The results of numerical taxonomy based on208 phenotypical features showed that all tested strains were divided into 3 groups above72% similarity level. They were fast growing rhizobia, slow-growing rhizobia and amoderate-slow-growing group (generation time was above 5 hr). Most of new isolatesfell in 5 distinctive subgroups, differing from all known species of root nodule bacteria.Three of the 5 new subgroups belonged to Rhizobium, One of them belonged toBradyrhizobium. Another moderate-slow-growers were similar with a proposed newspecies, R. tianshanense. The analysis of DNA-DNA hybridization indicated that one(subgroup 7) of the 3 fast growing subgroups belonged to Rhizobium loti, and the otherswere new DNA homologous groups, differing from all known species. The exacttaxonomic positions of these new subgroups will be determined by further studies.