Chloroplast genomes of seven species of Coryloideae (Betulaceae): structures and comparative analysis

Coryloideae is a subfamily in the family Betulaceae consisting of four extant genera: Carpinus, Corylus, Ostrya, and Ostryopsis. We sequenced the plastomes of six species of Corylus and one species of Ostryopsis for comparative and phylogenetic analyses. The plastomes are 159–160 kb long and possess typical quadripartite cp architecture. The plastomes show moderate divergence and conserved arrangement. Five mutational hotspots were identified by comparing the plastomes of seven species of Coryloideae: trnG-atpA, trnF-ndhJ, accD-psaI, ndhF-ccsA, and ycf1. We assembled the most complete phylogenomic tree for the family Betulaceae using 68 plastomes. Our cp genomic sequence phylogenetic analyses placed Carpinus, Ostrya, and Ostryopsis in a clade together and left Corylus in a separate clade. Within the genus Corylus, these analyses indicate the existence of five subclades reflecting the phylogeographical relationships among the species. The data offer significant genetic information for the identification of species of the Coryloideae, taxonomic and phylogenetic studies, and molecular breeding.