Comparative chloroplast genomic analysis of an important horticultural plant, Dendrobium sulcatum (Orchidaceae) and phylogenetic position in Dendrobium

The genus Dendrobium Sw. has great ornamental and medicinal values. However, species classification of this genus is very difficult because of their similar morphological characteristics. The complete chloroplast genome has been widely used as a useful molecular marker for resolving phylogenetic relationships in complicated or closely related species. Therefore, in this study, the complete chloroplast genome of Dendrobium sulcatum was sequenced, assembled and characterized, and compared with published samples of Dendrobium species to investigate its phylogenetic position. The complete chloroplast genome of D. sulcatum was 159,563 bp in length, with 130 genes, including 84 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. The total GC content of the whole genome was 37.14%. Phylogenetic analyses indicated that D. sulcatum is closely related to D. jenkinsii, D. lindleyi, D. exile, D. spatella, D. parciflorum, and D. hainanense. Furthermore, the D. sulcatum chloroplast genome and the 33 published samples were proven to be highly similar in genome size, gene content, and organization. The complete chloroplast genomes of Dendrobium exhibited typical quadripartite structures with lengths from 149,186 bp to 159,563 bp. This study provides useful genetic data of Orchidaceae and enhances our understanding about their phylogenic relationship and evolution.