The Straight Dope On The Genetics Of Cannabis

Cannabis sativa... or is it? Credit: Mr Green/Shutterstock

Botanists have gone where few have dared go before, exploring the genetics, taxonomy and evolution of marijuana. The findings may prove useful for differentiating between hemp grown for industrial purposes and that put to more recreational or medicinal purposes.

We have only rough estimates of how much marijuana is produced in total, let alone its commercial value. But with estimates around $2.6 billion in 2014 in the U.S. alone, it is fair to say that if any legal crop was this big a part of the economy, plenty of money would be spent to research its genetics in the quest to create better breeds.

Unsurprisingly, that is not the case for cannabis. Even low THC legal strains, grown for their fibers and known as hemp, exist in the shadow of illegal versions. "Even though hemp and marijuana are important crops, knowledge about cannabis is lacking because of its status as a controlled drug," said Dr. Jonathan Page of the University of British Columbia in a statement.

Page reports in PloS One that a study of 81 marijuana and 43 hemp samples showed cannabis to have genetics as confused as heavy users. “We show that marijuana and hemp are significantly differentiated at a genome-wide level, demonstrating that the distinction between these populations is not limited to genes underlying THC production,” Page and his co-authors report.

The cannabis genus has been categorized as three species: C. sativa, C. indica and C. ruderalis, but this might require adjustment.

Dealers, whether in or outside the law, market their products as having different effects, with Cindica promoted as being more relaxing than Csativa. However, Page found there was little correlation between the genetics of a sample and the way it was sold. "Cannabis breeders and growers often indicate the percentage of Sativa or Indica in a cannabis strain, but they are not very accurate," said Page.

Instead, the authors report, “We find a moderate correlation between the genetic structure of marijuana strains and their reported Csativa and Cindica ancestry and show that marijuana strain names often do not reflect a meaningful genetic identity.”

Hemp plants low in the THC responsible for marijuana's psychoactive effects are classified as being varieties of sativa, but the authors say, “We also provide evidence that hemp is genetically more similar to Cindica type marijuana than to Csativa strains.”

The paper notes that “Cannabis is one of humanity's oldest crops, with records of use dating to 6000 years before present...[but] the evolutionary and domestication history of Cannabis remains poorly understood.”

Studying a plant that has been so widely demonized has its difficulties. As the authors note, “There are limited repositories of hemp germplasm in international seedbanks.” Consequently, “We observe a putative Cindica marijuana strain from Pakistan that is genetically more similar to hemp than it is to other marijuana strains." The authors conclude that differences between hemp and smokable marijuana are greater than those within either category. Perhaps as medical use and legalization spreads, Page's work will be put to greater use.

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