Identification of Cistanche species (Orobanchaceae) based on sequences of the plastid psbA-trnH intergenic region

The dried succulent stems of Cistanche (Cistanche deserticola Y. C. Ma and Cistanche tubulosa Wight.) are one of the most widely used components of traditional Chinese medicines. However, it is often confused and substituted with the roots of Orobanche pycnostachya, Boschniakia rossica (Cham. & Schltdl.) Standl., Cistanche sinensis Beck, and Cistanche salsa (C. A. Mey.) Beck. In this study, we identified psbA-trnH regions from species and tested their suitable for the identification of the above mentioned taxa. The psbA-trnH sequences showed considerable variations between species and thus were revealed as a promising candidate for barcoding of Cistanche species. Additionally, the average genetic distance of psbA-trnH ranging from 0.077% to 0.743%. In contrast, the intra-specific variation among Cistanche species was found to be significantly different from those of other species, with percentages of variation studied ranged from 0% to 0.007%. The sequence difference between the psbA-trnH sequences of Cistanche species and Orobanche pycnostachya ranged from 0.979% to 1.149%. The distance between the Cistanche species and Boschniakia rossica ranged from 1.066% to 1.224%. Our results suggest that the psbA-trnH intergenic spacer region represent a barcode that can be used to identify Cistanche species and other morphologically undistinguishable species.