AbstractNineteen standard USDA strains reprenting three recognized soybean rhizobia，Sinorhizobium fredii，Bradyrhizobium japonicum and B．elkanii，were examined by restrietion fragment length Polymorphism (RFLP) analysis of 16S rRNA genes amplified by Polymerase chain reactin (PCR)．Four composite genotypes were obtained from the combined data of the RFLP analysis with three endonucleases,S.fredii,Bjaponicum,Belkanii Ⅱ and Ⅱa reference strains fell into these four genotypes respectively.No genotype was shared by two speciies.Therefore,16SrDNA PCR-RFLP is a rapid tool for the identification of soybean rhizobia.According to 16SrDNA PCR-FRLP,22 fast-growing and 19 slow-growing soybean rhizobia strains form China were identified to S.fredii and B.japonicum,respectively. The reference strains and wild type isolates were also examined by 16S~23S intergenic spacer PCRE－RFLP analysis.PCR results indicated that the length of the intergenic region between S.fredii and Bradyrhizobium sp.is different.All fast-growing S.fredii strains produced one large band (2.1kb),and all slow-growing Bradyrhi-zobium strains produced one smaller band (2.0kb).Based on 16S~23SRFLP analysis,22S.fredii isolate can be further separated into two "genotypes"that originated from two different regions in China;19B.japonicum were also characterized at strain level by REP (repetitive extragenic palindromic)and ERIC (enterobacterial repetitive intergenic consensus)PCR fingerprinting.