Low genetic diversity, limited gene flow and long-term genetic bottleneck effects in a threatened Gentianaceae species, Swertia przewalskii Pissjauk

Fresh leaves were dried in silica gel. DNA was extracted from the leaf tissues of all samples using the CTAB method.The DNA extraction and Double Digest Restriction-site Associated DNA Sequencing (ddRAD Sequencing) technology were employed to obtain genetic data from these samples. The DNA was diluted to a concentration of 10 ng/μL and digested with EcoRI and MseI enzyme pair.

A series of procedures, including end repair and phosphorylation, a-tail addition, sequencing connector addition, purification, and PCR amplification, were carried out to finish the ddRAD library construction. The sequencing platform Illumina HiSeq X-ten at BENAGEN Co. Ltd (Wuhan, China) was employed to generate 150 bp paired-end reads for each sample (~ 0.5 Gb data for each).