Résumé
This study was aimed to show the extraction research of cpDNA in Gentiana straminea Maxim. and G. crassicaulis Duthie ex Burk., which will increase the knowledge about the chloroplast genome sequence characteris-tics, understand its genetic diversity and improve the efficiency of breeding schemes. G. straminea Maxim. and G. crassicaulis Duthie ex Burk. were taken as study objects. The improved sucrose-gradient centrifugation and purifica-tion methods were used to obtain the cpDNA, measure the concentration, detect the OD value, and amplify the ITS2 sequence to verify the nucleus pollution. The results showed that the high quality and purity cpDNA (0.1 - 0.4 μg/10 g) was demonstrated without other pollution after ITS2 sequence amplification, which met to the subsequent effi-cient sequencing of chloroplast genomes. The purity and mass have an important influence on the accuracy and cred-ibility of the cp genome sequencing. It was concluded that this study improved the sucrose-gradient centrifugation and purification with great effect of the purity and mass of cpDNA, and guaranteed the obtaining of complete cpDNA of Gentiana.