SHARE

Cannabis is one of the oldest domesticated plants, but we know surprisingly little about it. That’s because, given marijuana’s status as an illicit substance in most of the world, gaining permission to conduct research into its medicinal properties or genetic heritage has been notoriously difficult. Now a team of Canadian researchers has peered into the plant’s genome to understand the different species that may account for marijuana’s famous variations, and lend some insight into the plant’s ancestry. The study was published yesterday in PLOS One.

If you go into a medical marijuana shop (or watch any stoner movie ever), you know that different strains of marijuana are supposed to have different effects on the body. They can be flavorful, or potent; induce relaxation or hallucinations. Marijuana farmers often work on the assumption that plants with a particular genetic ancestry have one quality or another; dealers advertise their strains’ qualities by touting their genetic makeup, claiming that strains with more DNA from the C. sativa species make for a more “euphoric” high, for example.

The researchers sequenced the genes of 81 samples of marijuana and 43 samples of hemp, a different variety of the same plant with less THC, the chemical responsible for pot’s characteristic effects. The samples were all part of three species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. The researchers found that most marijuana samples were from two species, sativa and indica. And though hemp was genetically distinct from marijuana in more genes than just those that control THC production, it was genetically similar to the indica marijuana strains. “Whether this points to different origins for hemp and marijuana, or is the result of human selection for different uses, is not clear,” says Jonathan Page, one of the study authors.

But, importantly, the researchers found a lot of discrepancy between a sample’s species reported by marijuana growers and those shown by the genetic tests. “Cannabis breeders and growers often indicate the percentage of sativa or indica in a cannabis strain, but they are not very accurate,” Page said in a press release. The researchers highlighted one strain, called Jamaican Lamb’s Bread, that its vendors claimed to be fully C. sativa but was actually 100 percent C. indica. That might mean that the relationship between certain qualities in marijuana and the species may not be so straightforward, after all.

The researchers note that this has significant legal implications. While hemp is grown legally for clothing or paper, marijuana is illegal in many places. If an individual is caught with the plant, it may be difficult for officials to tell the difference between the two if their genes are similar.

This work provides good insight into the genetics of marijuana now, but doesn’t say much about cannabis’ ancestry. “We found evidence that there are genetic differences between C. sativa and C. indica, however more research needs to be done to investigate whether these genetic differences result in marijuana strains with differing therapeutic applications,” Page says. The scientists hope to compile a more thorough classification system for marijuana and a more detailed view of the plant’s ancestry in future studies.

MORE TO READ