Species identification in complex groups of medicinal plants based on DNA barcoding: a case study on Astragalus spp. (Fabaceae) from southwest China

Abstract

Species from the genus Astragalus L. (Fabaceae) are distributed throughout the world, with southwest China being one of the distribution centers of this genus. Many Astragalus species are used by local Chinese people as traditional medicines for enhancing immunity. However, the complexity of morphological characters in many Astragalus species makes it difficult to correctly identify them. DNA barcoding is a useful tool for species identification based on standardized DNA markers. In this study, internal transcribed spacer (ITS) region and three chloroplast regions (matK, rbcL, and trnH–psbA) were used for the identification of Astragalus species from SW China. The ITS region showed a high success rate of PCR amplification and bidirectional sequencing, as well as a high discriminatory ability (72%). The matK region also possessed relatively perfect university and had a high discriminatory ability (61%); while the rbcL region, the most popular cpDNA marker, showed good university but low discriminatory ability (44%). We found that the trnH–psbA region was not suitable for identifying Astragalus species because of its low success rate of DNA sequencing. In the studied species, combination of multiple DNA barcodes could improve the discriminatory ability. The ITS region was able to identify frequently used Astragalus species in SW China, such as A. yunnanensis, A. acaulis, A. bhotanensis, and A. camptodontoides, and we concluded that this region could be listed as the core barcode for species identification of medicinal Astragalus species from SW China.