Chloroplast markers for the Malvaceae and the plastome of Henderson's checkermallow (Sidalcea hendersonii S.Wats.), a rare plant from the Pacific Northwest.

OBJECTIVE: Sidalcea is a genus of flowering plants restricted to the west coast of North America, commonly known as checkermallows. Remarkably, of the ~ 30 recognized species, 16 are of conservation concern (vulnerable, imperilled or critically imperilled). To facilitate biological studies in this genus, and in the wider Malvaceae, we have sequenced the whole plastid genome of Sidalcea hendersonii. This will allow us both to check those regions already developed as general Malvaceae markers in a previous study, and to search for new regions. RESULTS: By comparing the Sidalcea genome to that of Althaea, we have identified a hypervariable circa 1 kb region in the short single copy region. This region shows promise for examining phylogeographic pattern, hybridization and haplotype diversity. Remarkably, considering the conservation of plastome architecture between Sidalcea and Althaea, the former has a 237 bp deletion in the otherwise highly conserved inverted repeat region. Newly designed primers provide a PCR assay to determine presence of this indel across the Malvaceae. Screening of previously designed chloroplast microsatellite markers indicates two markers with variation within S. hendersonii that would be useful in future population conservation genetics.