Barcoding Plant DNA

There are an estimated 400,000 plant species on the planet. An international team of scientists has agreed on a standard "DNA barcode" for plants that will allow botanists to identify species quickly and easily.

Their hope is that this agreement will lead to the formation of a global plant DNA database which can be shared by the entire scientific community. The barcodes are expected to a number of uses, one of which can be utilized in identifying the illegal plant trade in endangered species.

"Identification is important," said lead author Dr Peter Hollingsworth, head of genetics and conservation at the Royal Botanic Garden, Edinburgh, Scotland. "It is the link between a given plant and the accumulated information available for that species. It is not possible to know whether a plant is common or rare, poisonous or edible, being traded legally or illegally, unless it can be identified."

The "barcode" will allow plants to be identified from tiny fragments.

Co-author Robyn Cowan, a conservation geneticist at Royal Botanic Gardens, Kew, said the development would allow larger areas to be surveyed more quickly.

"We are short of botanists and their expertise in a lot of places around the world," she told BBC News. "This is one way that we will be able to increase our information and understanding of biodiversity and where things are growing around the world."

The DNA databases will save on manpower by eliminating the need for a specialist botanist to be at the site. Samples can now be sent back to a lab for processing and identification, thus saving the need (and expense) of having a specialist botanist at the location.

"And there are also more applied uses; in forensics, for example," she said. "We have also done a little bit of preliminary work on Chinese herbal medicines. We have been checking that people are getting what they should be getting in terms of medication and active ingredients. One thing that is really good about this process is that you can identify plants from different life stages or just fragments of plants. For example, if you are looking at trade in endangered species and you have things that are not flowering, or are just seedlings, it can be incredibly difficult to positively identify the plants."

Barcodes will be used to catalogue the world's 100,000 tree species.

"The DNA in land plants behaves, in some ways, quite differently to DNA in animals, so we were not able to use the same [marker]," she said. "We had to search for the best solution because a barcode needs certain characteristics.

It needs to be technologically easy to deal with; it needs to be readily obtainable from degraded material (very old samples or fragments); and it needs to be variable enough between species to be able to separate them but not too variable within species. The team assessed seven potential "barcodes", testing them on a common set of samples. Eventually, they chose two regions of DNA to form the plant barcode. The conclusion we have come to will give us a good basic barcode to use."

The four-year project was carried out by the Consortium for the Barcode of Life (CBOL) Plant Working Group, which consists of 52 scientists from 10 nations.

David Schindel, executive secretary of CBOL, applauded the breakthrough: "The selection of standard barcode regions has been a slow and difficult process because of the complex nature of plant genetics."

One use of the plant barcoding will be to build a DNA database for the world's 100,000 tree species, many of which are deemed to be of either conservational or economic importance.