Twin Brothers, Indentical In Looks-Distinguishable by DNA

Hemp or Pot? DNA reveals all!

Hemp is a really useful plant with potential applications that include paper, textiles, food, medicine, and chemicals. There’s one drawback, though: its highly lucrative “evil twin” , known variously as marijuana, weed, or dagga.

Fortunately for supporters of hemp as a legitimate crop, there’s a new technique to distinguish it from its illegal relative.

Hemp belongs to the same species, Cannabis Salvia, as marijuana, and although the plants differ in levels of the psychoactive drug tetrahydrocannabinol (THC), they are otherwise difficult to tell apart. Or they were, until two University researchers found a way.

George Weiblen, an assistant professor of plant biology at the, University of Minnesota, along with a colleague, decided to investigate the genetics of hemp and its marijuana twin after the potential of hemp as a crop was publicised.

Its uses include paper, textiles, building materials, food, medicine, paint, detergent, varnish, oil, ink, and fuel. A natural for northern climates, the hardy plant matures in three months, needs no pesticides and only moderate fertiliser.

Using a new DNA "fingerprinting" technique called AFLP (amplified fragment length polymorphism), the team has become the first to unequivocally separate hemp plants from marijuana plants with genetic markers.

The technique holds promise for distinguishing different cultivars (domesticated plant lines) in American criminal cases. It may also prove useful where the cultivation of hemp is permitted, but marijuana is illegal – for instance, Canada and some European countries.

Said Weiblen: "We think this technique has the potential to distinguish marijuana varieties as well. It has implications not just for separating hemp from marijuana in countries where hemp cultivation is permitted, but in establishing origins of seized drugs and, therefore, conspiracy in drug distribution networks. It also could be used in criminal defences against claims of conspiracy."

In tests with three different cultivars of hemp and one of marijuana, the DNA fingerprints of all the cultivars were distinct and non-overlapping.

The research party found that the, AFLP, technique generated hundreds of genetic markers that together established separate identities for each of the four cultivars.

The new technique is an improvement on previous means of separating the two types of Cannabis.

For decades it has been possible to identify THC chemically, but the drug is not present in all plant tissues or throughout a plant's life cycle. And other researchers have found that genetic markers known as "short tandem repeats," which are used to identify individuals in paternity and criminal cases, lack the power to distinguish Cannabis cultivars unequivocally.

Weiblen wants to screen a wider range of Cannabis cultivars to refine the technique and is also working to identify regions of the Cannabis genome responsible for drug content in marijuana.

If enough can be learned about the genome, it may one day be possible to produce an entirely drug-free hemp plant that looks different from marijuana.

[ Hemp Werx source: Popular Mechanics- 23 May 2006 ]