Abstract: For exploiting and making use of rhizobium species resources of planting leguminous trees in south China,the full-length 16S rDNA sequences of representative strains HJ06 and JJ06 of two rhizobia,isolated from Acacia crassicapa and A.cincinnata in south China,were determined.These sequences were compared with all known rhizobia and related bacteria and an unrooted phylogenetic tree was produced.In this tree, HJ06 clusterd together with some Rhizobium species and had above 95% similarity.JJ06 formed a cluster with Mesorhizobium species and had above 97% similarity.The results indicated that strain HJ06 placed in the Rhizobium and strain JJ06 was identified as Mesorhizobium.Overall,the results demonstrated a diversity and complicacy of rhizobial strains nodulting Acacia spp.tree,which was introduced from overseas to south China.