The complete chloroplast genome of Inula britannica and the phylogeny and evolution of the genus Inula

Abstract Background Inula britannica is an important medicinal plant of Asteraceae. Its dry capitulum has been used as a traditional Chinese herbal medicine, which had the functions of treating edemas, reduction in nausea, and preventing vomiting. There have not been many chloroplast genome studies. Methods and results we de novo assembly of the complete chloroplast genome of I. britannica. The genome was characterized and compared with the other five Inula species. The chloroplast genome of I. Britannica was 150,774 bp long. It showed a typical quadripartite structure, containing a large single-copy region, a small single-copy region, and a pair of inverted repeat regions, which were 82,451 bp, 18,423 bp, and 24,950 bp long, respectively. It encoded 109 unique genes, including 79 protein-coding genes, four rRNA genes, and 26 tRNA genes. Forty-nine long repetitive sequences and 69 simple sequence repeats were identified in the I. britannica chloroplast genome. We detected 14 hypervariable regions and identified six pairs of genus-specific DNA markers, which could differentiate congeneric species. Phylogenetic analysis showed that I. britannica was closely related to I. janopinca and I. linariifolia. Ancestral character state reconstruction indicated transitions from long spur to other petal types in Inula. Results from divergence time analysis showed that Inula diversified in the late Pliocene (~ 3.245 Mya). Conclusion In this study, we sequenced and assembled the chloroplast genome of I. Britannica. Phylogenomic analysis has identified species closely related to I. britannica, which will help determine its evolutionary relationships and taxonomic status.