Friday, November 23, 2012

Agarwood barcoding

Aquilaria crassna
Aquilaria crassna is a tree species that has been of great ethnobotanical importance to people throughout the Greater Mekong region and beyond. Its heartwood and resin are highly valued commodities that have been transported along long-established trade routes for thousands of years. However, this species has now become Critically Endangered, owing to over-exploitation.

The wood from Aquilaria crassna (Agarwood) contains aromatic resin, known as ‘gaharu’. This is produced by the tree in response to injury if the production of callus tissue is inhibited. It acts as a chemical barrier to attack by insects and fungi. However, under natural conditions gaharu is not produced by trees at all. This resin is often used in temples as perfume wood. The wood can also be distilled to yield a valuable essential oil, which is widely used in Chinese and Southern Asian medicine and also in the Middle East for making perfumes and cosmetics. 

Currently the majority of the wood comes from wild populations and there is now a very real danger this species may become extinct if wild harvesting continues at the current rate. To conserve this species, it is vital that this plant becomes more widely grown in cultivation, to reduce the pressure on the few wild populations that remain. Cultivation requires high quality seed and especially in Vietnam there is concern that a range of hybrid species or other members of the genus could lead to production loss and disappearance of the original species. Proper species identification starts with the seeds used and Vietnamese researchers have now tested if DNA Barcoding could help. Not surprisingly it worked quite well and one of the official plant markers, rbcL along with ITS was tested most effective.

Probably it needs to reemphasized that DNA Barcoding cannot identify hybrids (oh well, I probably should say mostly, but that's a different story...) but it can help to distinguish between seeds of different Aquilaria species obtained in the wild and destined to be used in cultivation.

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