Abstract: The genetic diversity among 20 Cymbidium accessionswas investigated by RAPD markers and PCR-RFLP analyses of organellar DNAs. In RAPD analyses, the amplified roducts of 36 primers (72.0% ) were polymorphic. The RAPD-based genetic similarity (GS) among 20 Cymbidium accessions ranged from
01503 to 01765, with the mean of 0.598. Based on genetic similarity matrix resulting from RAPD makers, the genetic relationships among 20 Cymbidium accessions were estimated by UPGMA ( unweighted pair group method with arithmetic means) clustering analysis. It was found that all 20 Cymbidium accessions could be distinguished by RAPD markers. In cpDNA PCR-RFLP analyses, 6 out of 7 markers (87.5% ) could produce one or more than one distinct bands by direct electrophoresis in 2% agrose gels. After the amplified products were digested by 7 restriction enzymes, a total of 53 bandswere detected in 19 cpDNA PCR-RFLP marker / enzyme combinations, among which 37 bands (69.8% ) were polymorphic. The cpDNA PCR-RFLP-based genetic similarity (GS) among 20 Cymbidium accessions ranged from 0.571 to 0.949, with the mean of 0.766. Of the 8 mtDNA PCR-RFLP markers, 3 markers (37.5% ) could p roduce one distinct band with no polymorphism detected by direct electrophoresis in 2% agrose gels. After the amplified productswere digested by 7 restriction enzymes, a total of 33 bands were detected in 10 mtDNA PCR-RFLP marker/enzyme combinations,among which 21 bands (63.6% ) were polymorphic. The mtDNA PCR2RFLP2based genetic similarity (GS) among 20 Cymbidium accessions ranged from 0.634 to 1.000, with the mean of 0.829. These results suggested that relatively higher level of genetic polymorphism in Cym bidium could be detected by RAPD markers, whereas relatively lower level genetic polymorphism could be estimated by mtDNA PCR-RFLP markers.

Key words: Cymbidium, RAPD, PCR-RFLP, cpDNA, mtDNA