Plastome Analysis and Phylogenetic Reconstruction of Iris Speci es in China

Background Iris is a group of perennial herb with important horticultural value. There are over 300 species of Iris species worldwide, and China has approximately 70 species. A series of studies utilized chloroplast fragments to explore the phylogenetic relationships of Irises, but the number of species and the reliability of the results of most studies were not satisfied. We sequenced and assembled the chloroplast genomes of 17 species of Iris , and downloaded 62 available data from public database to construct the most complete phylogenetic evolutionary tree and analyze the evolution and origin relationship of genus Iris. Results The 79 Iris chloroplast genomes exhibit highly similar genome size, gene content, and order. The Iris chloroplast genomes show typical quadripartite structures with lengths from 150,169 bp to 155,878 bp. All plastomes exhibit typical quadripartite structure, consisting of a large single-copy (LSC) region, a small single-copy (SSC) region, and two inverted repeats (IRa and IRb). Phylogenetic results support Iris as a monophyletic group, and indicate that Iris was divided into three major clades. The divergence times indicate that Iris diverged from Crocos at early Eocenein. Bearded and rhizomelic might be the original traits of Iris , and then independently evolve into beardless, bulbous or tuberous. Conclusion Our study supports the present taxonomic treatment at the subgenus level for Iris species, and demonstrates the validity of phylogenetic resolution using whole chloroplast genome sequences. We also prove that the Iris plastome developed molecular markers can help us better identify and understand the evolutionary history of Iris species in the future.