Aquilaria sinensis (Lour.) Gilg is an evergreen tree and produces agarwood used for incense and as a uniquely precious medicine. It is in danger of disappearing due to illegal logging and its identification and protection is crucial. However, it is difficult or impossible to distinguish A. sinensis from other species of the genus Aquilaria Lam. and its closely related genus Gyrinops Gaertn. based on wood anatomical characteristics. Probably, DNA barcoding technology might provide an improvement in species identification. In this study, wood samples were tested, which were submitted to high-temperature drying and were stored for a long period in a xylarium. The factors should be identified that hinder the efficiency of wood DNA extraction from this species. The results indicate that the DNA from the wood tissues could be successfully amplified, apart from some DNA regions from the heartwood of the dried samples and the xylarium samples. The DNA sequences from the wood tissues mostly matched with the sequences of A. sinensis deposited in the GenBank. Moreover, analyses of phylogenetic trees based on trnL-trnF and ITS1 regions indicated that the wood tissues in the tests clustered together with the A. sinensis species from the GenBank, with bootstrap values of 74% and 94%, respectively. Consequently, it is feasible to identify A. sinensis wood on a species level based on the DNA barcoding technology.

DNA barcoding has been proposed as a useful tool for forensic wood identification and development of a reliable DNA reference library is an essential first step. Xylaria (wood collections) are potentially enormous data repositories if DNA information could be extracted from wood specimens. In this study, 31 xylarium wood specimens and 8 leaf specimens of six important commercial species of Pterocarpus were selected to investigate the reliability of DNA barcodes for authentication at the species level and to determine the feasibility of building wood DNA barcode reference libraries from xylarium specimens. Four DNA barcodes (ITS2, matK, ndhF-rpl32 and rbcL) and their combination were tested to evaluate their discrimination ability for Pterocarpus species with both TaxonDNA and tree-based analytical methods. The results indicated that the combination barcode of matK + ndhF-rpl32 + ITS2 yielded the best discrimination for the Pterocarpus species studied. The mini-barcode ndhF-rpl32 (167–173 bps) performed well distinguishing P. santalinus from its wood anatomically inseparable species P. tinctorius. Results from this study verified not only the feasibility of building DNA barcode libraries using xylarium wood specimens, but the importance of using wood rather than leaves as the source tissue, when wood is the botanical material to be identified.