Characteristics of the complete chloroplast genome of <i>Swertia divaricata</i> Harry Sm. (Gentianaceae) and its phylogenetic inference

Swertia divaricata Harry Sm., 1965, (Gentianaceae) is a perennial herb endemic to Northwest Yunnan, China, belonging to the species-rich genus Swertia. It possesses unique morphological features but its systematic position remains uncertain. To determine its phylogenetic placement, the complete plastid genome of S. divaricata was assembled utilizing high-throughput sequencing data. The genome is circular, spanning 152,073 bp, and comprises a large single-copy (LSC) region of 82,470 bp, a small single-copy (SSC) region of 18,153 bp, and two inverted repeats (IR) regions, each 25,725 bp. A total of 130 genes were annotated, including 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The plastome of S. divaricata exhibits a structure and gene composition highly similar to those of other Swertia plastomes. Phylogenetic analysis indicated that S. divaricata is closely related to S. erythrosticta, sister to a subclade comprising species from sections Swertia and Apterae. The plastome sequence described herein constitutes a valuable contribution to phylogenetic and evolutionary research on Swertia.叉序獐牙菜（Swertia divaricata Harry Sm.，1965）隶属于龙胆科（Gentianaceae），是中国云南西北部特有的多年生草本植物，属于物种丰富的獐牙菜属（Swertia）。该种具有独特的形态特征，但其系统分类位置迄今尚未明确。为明确该种的系统发育定位，本研究基于高通量测序数据组装获得了叉序獐牙菜的完整质体基因组。该基因组呈环状结构，全长152073 bp，包含1个长单拷贝区（large single-copy, LSC），长度为82470 bp；1个短小单拷贝区（small single-copy, SSC），长度为18153 bp；以及2个反向重复区（inverted repeat, IR），每个区域长度为25725 bp。共注释得到130个基因，其中包括85个蛋白编码基因、37个转运RNA（transfer RNA, tRNA）基因以及8个核糖体RNA（ribosomal RNA, rRNA）基因。叉序獐牙菜的质体基因组结构与基因组成，与其他獐牙菜属植物的质体基因组高度相似。系统发育分析结果显示，叉序獐牙菜与红纹獐牙菜（Swertia erythrosticta）亲缘关系密切，为包含獐牙菜组（section Swertia）和无瓣组（section Apterae）物种的亚分支的姊妹群。本研究报道的质体基因组序列，可为獐牙菜属的系统发育与进化研究提供重要参考价值。