Molecular identification of Aquilaria species with distribution records in China using DNA barcode technology

Aquilaria species is one of the main plant resources that produce agarwood, which containing black resin with important economic and medicinal values. There are about 15 species known to the genus around the world, but only two can be found in China, i.e. A. sinensis and A. yunnanensis. In this study, A. sinensis and A. yunnanensis that endemic respectively to Hainan and Yunnan were sampled, on the basis of the investigation and observation of their main morphological features in plantation. Five primers, i.e. ITS2, matK, trnL-trnF1, trnL-trnF2, and trnH-psbA, were eventually selected for DNA barcoding. The results showed that the seed surface of A. sinensis is smooth or sparsely pubescent, and the seed appendages were long. While the seed surface of A. yunnanensis is densely covered with yellow hairs and the seed appendages are short. The trnL-trnF1 sequence fragment has significant intraspecific and interspecific genetic distances. However, the species identification success rate of ITS2+matK combination was finally screened to be the highest, which was verified by the BBA method of TaxonDNA. The phylogenetic trees cluster analysis revealed that the classification of A. sinensis and A. yunnanensis is significant, and there is geographic isolation between the two species. Therefore, on the premise of accurate identification of plant morphological characters, ITS2+matK combination can be used to accurately identify the Aquilaria species in China.