Characterization of the chloroplast genome of medicinal herb Polygonatum cyrtonema and identification of molecular markers by comparative analysis.

Polygonatum cyrtonema Hua is a traditional Chinese herb medicine, and it is widely distributed in China. The intrageneric taxonomy and phylogenetic relationships within Polygonatum have long been controversial due to their morphological similarity and lacking special DNA barcodes. In this paper, the complete chloroplast genome is a relatively conserved quadripartite structure including a large single copy region of 84 711 bp, a small single copy region of 18 210 bp, and a pair of inverted repeats region of 26 142 bp. A total of 342 simple sequence repeats were identified, and most of them were found to be composed of A/T, including 126 mono-nucleotides and 179 di-nucleotides. Nucleotide diversity was analyzed and eight highly variable regions (psbl∼trnT-CGU, atpF∼atpH, trnT-GGU∼psbD, psaJ∼rps20, trnL-UAG∼ndhD, ndhG∼ndhl, ndhA, and rpl32∼ccsA) were identified as potential molecular markers. Phylogenetic analysis based on the whole chloroplast genome showed that P. cyrtonema, within the family Asparagaceae, is closely related to Polygonatum sibiricum and Polygonatum kingianum. The sequence matK, trnT-GGU & ccsA, and ndhG∼ndhA were identified as three DNA barcodes. The assembly and comparative analysis of P. cyrtonema complete chloroplast genome will provide essential molecular information about the evolution and molecular biology for further study.