Abstract
The identification of Aquilaria species from their resinous non-wood product, the agarwood, is challenging as conventional techniques alone are unable to ascertain the species origin. Aquilaria is a highly protected species due to the excessive exploitation of its precious agarwood. Here, we applied the DNA barcoding technique to generate barcode sequences for Aquilaria species and later applied the barcodes to identify the source species of agarwood found in the market. We developed a reference DNA barcode library using eight candidate barcode loci (matK, rbcL, rpoB, rpoC1, psbA-trnH, trnL-trnF, ITS, and ITS2) amplified from 24 leaf accessions of seven Aquilaria species obtained from living trees. Our results indicated that all single barcodes can be easily amplified and sequenced with the selected primers. The combination of trnL-trnF+ITS and trnL-trnF+ITS2 yielded the greatest species resolution using the least number of loci combination, while matK+trnL-trnF+ITS showed potential in detecting the geographical origins of Aquilaria species. We propose trnL-trnF+ITS2 as the best candidate barcode for Aquilaria as ITS2 has a shorter sequence length compared to ITS, which eases PCR amplification especially when using degraded DNA samples such as those extracted from processed agarwood products. A blind test conducted on eight agarwood samples in different forms using the proposed barcode combination proved successful in their identification up to the species level. Such potential of DNA barcoding in identifying the source species of agarwood will contribute to the international timber trade control, by providing an effective method for species identification and product authentication.
Highlights
Aquilaria Lam., an endangered genus in the family Thymelaeaceae, is well known for its production of a fragrant non-wood product generally known as ‘agarwood’
A total of 103 sequences from NCBI GenBank database were downloaded, comprising of maturase K (matK) (12), ribulose-bisphosphate carboxylase (rbcL) (13), rpoC1 (3), psbA-trnH (15), trnL-trnF (24), internal transcribed spacer (ITS) (22), and ITS2 (14) sequences (Table 4)
The barcode proposed by Rauntenbach [37], i.e. the combination barcode rbcL+trnL-trnF +ITS (LC-y), had “all species barcodes” results identical to the trnL-trnF+ITS (LC-i) combination as we demonstrated in this study (Table 7)
Summary
Aquilaria Lam., an endangered genus in the family Thymelaeaceae, is well known for its production of a fragrant non-wood product generally known as ‘agarwood’. The genus Aquilaria was further classified in Appendix II of the Convention on International Trade in Endangered Species of Fauna and Flora (CITES) as “Endangered”. This effectively placed all species in the entire Aquilaria genus under CITES protection, which among others requires trade permits for export purposes [3]. These classifications demonstrate that the agarwood trade is closely monitored by international regulators to ensure that such activity will not continue to be detrimental to the continued existence of these species in the wild
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
