The complete chloroplast genome of <i>Scrophularia kakudensis</i> and a comparative analysis of <i>S. kakudensis</i> and <i>S. cephalantha</i>

The genus Scrophularia L. (Scrophulariaceae) comprises 200–270 species worldwide and is a taxonomically challenging lineage, displaying morphological diversity and hybridization. S. kakudensis is morphologically similar to the closely related taxa S. kakudensis var. microphylla, S. pilosa, and S. cephalantha. Therefore, the purpose of this study was to sequence the chloroplast (cp) genome of S. kakudensis using next-generation sequencing and compare it to those of related taxa. The complete cp genome sequence of Scrophularia kakudensis was found to be 152,355 bp long, consisting of a pair of inverted repeats of 25,485 bp that separate a large single-copy (LSC) of 83,479 bp from small single-copy regions of 17,909 bp. The cp genome contained 78 protein-coding genes, 30 tRNAs, and four rRNAs. A phylogenetic analysis based on 78 protein-coding genes from six Scrophularia species showed S. kakudensis and S. cephalantha formed with 100% bootstrap values. We compared the complete cp genomes of S. kakudensis and S. cephalantha and identified seven sequence divergence regions: matK/rps16, rps16/trnQ, trnS/trnG, rpoB/trnC, trnS/trnG, rpl32/trnL, and ndhD/psaC. These regions may be useful for determining the phylogenetic relationships among S. kakudensis-related species.