Although Populus (Saliaceae) is an important group of forest trees in the sense of economy, ecology and scientific researches, few is known about the structural and sequence variation of chloroplast genome across the genus. We sequenced and characterized the complete chloroplast genome of the Chinese aspen (Populus adenopoda), and made comparative analyses of the structure variation of the chloroplast genomes of P. adenopoda and other 11 poplars. The P. adenopoda chloroplast genome is 158,591bp in length, exhibits a typical quadripartite structural organization, consisting of a LSC region of 84,634 bp, two IR regions of 27,667 bp and a SSC region of 18,623 bp. Comparison of the cp genome structure and gene order to those of the 12 Populus species indicated that the chloroplast genomes of this genus are rather conservative, only six large deletions or insertions were found across the whole genome. Phylogenetic analysis demonstrated that the 12 Populus species clustered into three well-supported clades, and Chinese aspen is most closely related to the white poplar, P. alba. Our work will better our understating of the evolutionary history of Populus, and will be useful to future population genetics and other molecular ecology studies of poplars based on chloroplast DNA sequences.
