DNA barcoding used for the first time to identify genus Caragana in legume family

The genus Caragana in the legume family is ecologically and pharmacologically important. Caragana plays a key role in the cold desert ecosystem throughout the Asian continent. However, accurate identification of taxa in the genus has been challenging.

In a study published in Journal of Systematics and Evolution, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences sought to establish a DNA barcoding standard to enable reliable identification of Caragana species, which will aid in quality control procedures especially for highly fragmented herbal materials.

The researchers conducted the most comprehensive taxon sampling of this genus. Using three analytical approaches (i.e., Pairwise Genetic Distance, Sequence Similarity and Phylogenetic Tree method), they evaluated the performance of four DNA barcoding regions, nrITS, trnH-psbA, matK, and rbcL.

They found that the nuclear ITS region was the most accurate and efficient barcode for distinguishing Caragana accessions/species. When used alone or in combination with trnH-psbA, it had the highest discrimination rate and can distinguish between Caragana species.

Unexpectedly, the previously recommended universal plant barcode rbcL + matK markers were ineffective as identifiers for Caragana species. Therefore, the researchers recommend the ITS alone or the concatenation of two regions (trnH-psbA + ITS) as plant barcodes in Caragana.

"To our knowledge, the present study is the first attempt to use DNA barcoding for Caragana and its relatives," said Liu Hongmei of XTBG.