DNA Barcoding Of The Genus Dolomiaea (Asteraceae)

Dolomiaea (Asteraceae), is an endemic genus mainly distributed in the Qinghai-Tibetan Plateau and adjacent regions, and plays an important role in traditional herbal medicine in China. However, the interspecific classification and species relationships in this genus remain problematic, which are difficult to discriminate by morphological characteristics of those plant. DNA barcoding as a new and an effective method of molecular biology are expected to medicinal plants of Dolomiaea to bring a new dawn. In the present study, we used neighbor-joining (NJ)、 Bayesian inference (BI) and TaxonDNA three different analytical methods to tested the universality and the discrimination power of five chloroplast markers matK (M), rbcL (R), trnH-psbA (H), trnL-F (L) and psbK-psbI (P), one nuclear barcode marker (ITS) and their combinations among 122 samples representing 15 species of Dolomiaea. The results showed that all these DNA markers, except matK marker the other single markers exhibited high primer universality in Dolomiaea; three different analytical methods show that the TaxonDNA method acquired the highest level of species discrimination rates and the other two methods (NJ, BI) showed little difference of species discrimination rates; Among all single barcode candidates, the nuclear ITS marker showed the most variable sites, larger interspecific variation and the highest rate of species discrimination (73.30%-73.43%), progressively lower for the other five chloroplast markers of species discrimination rates:psbK-psbI (53.30%-64.06%)> matK (46.7%-54.68%)> trnL-F (40.0%-59.37%)> trnH-psbA (33.30%-59.37%)> rbcL (28.12%-33.30%); Of the 27 combinations of markers, matK+rbcL as recommended by the Consortium for the Barcode of life (CBOL,2009) showed relative higher rate of species discrimination 73.30%-73.43%, while the species identification rate of the combination matK+ITS reached maximum value 80.0%-90.62%, almost equal to all single barcode combinations of the discrimination rates. At last, based on "Best match" analysis of the TaxonDNA, the combination matK+ITS of chloroplast and nuclear markers successfully identified 13 of 15 species of Dolomiaea (90.62%), we suggested the combination matK+ITS markers as the DNA barcodes of this genus. In this case study, DNA barcoding is a convenient technique and provides a reliable and effective mean for the discrimination of Dolomiaea species.