A novel rhizobial group cluster 9 defined in previous research Tan Z. Y., Wang E. T., Peng G. X. Zhu M.E., Martinez-ROMERO E Chen W. X. (1999) Int J Syst Bacteriol 49 1457-1469 was further characterized by determination of DNA base composition whole-cell protein SDS-PAGE analysis DNA-DNA hybridization 165 rRNA gene sequencing and host specificity These isolates were collected from the wild legumes Amphicarpaea trisperma Coronilla varia and Gueldenstaedtia multiflora growing in arid and semi-arid regions in north-wesern China lsolated within cluster 9 grouped into a single cluster above a similarity level of 90.6% in a cluster analysis based on protein SDS-PAGE and they were differentiated from defined rhizobial species comparative analysis of 165 rRNA gene sequences showed that isolate CCBAU 71623, representing cluster 9 was most related to Rhizobium gallicum and Rhizobium mongolense The DNA-DNA homologies were lower thatn 42.4% among cluster 9 and defined species including R. gallicum and R. MONGOLENSE Theese data indicated that cluster 9 was a unique genomic species lsoateds within this cluster could share their host plants They clould nt nodulate Galega orientalis and Leucarena leucocephala and formed inefeective nodulels on phaseolus vuaris This Group could also be differentiated from defined species by phenotypic characteristics it is therefore proposed as a new species Rhizobium yanglingense with isolate CCBAU 71623 as the type strain.