ITS2, a Better DNA Barcode than ITS in Identification of Species in Artemisia L.

Objective To select a more suitable DNA barcode to identify the species in Artemisia L. Methods ITS, ITS2, and three other major universal barcode candidates (matK, rbcL, and psbA-trnH) were evaluated in the identification efficiency using a total of 1433 sequences downloaded from GenBank representing 343 species in Artemisia L. ITS and ITS2 were evaluated in the PCR and sequencing rate, sequencing peak quality (Q value), and misread rate. One hundred and twelve A. annua samples were collected from 11 populations across over China, which were amplified with universal primers on the ITS and ITS2 regions. Results ITS and ITS2 shared a higher identification efficiency and exhibited 71.43% and 64.11% detectability at the species level, respectively. The Q values of ITS and ITS2 showed that the direct PCR sequencing data were reliable for the ITS2 region and ITS exhibited poor sequencing trace quality. In certain sites, the ITS sequences exhibited reading ambiguities and errors, indicating that the misread and deletion sites in the ITS region would incorrectly inflate the identification ratio. Conclusion ITS2 is a suitable barcode for identification of species in Artemisia L., which enlarges the optimal range of divergence levels for taxonomic inferences using ITS2 sequences.