According to a new cannabis genomics study by the University of Minnesota and hemp breeding company Sunrise Genetics, high-CBD plants get approximately 90% of their genes from marijuana.

CBD, or cannabidiol, is a chemical found in marijuana and in hemp. CBD does not cause a high and is often sold as a dietary supplement or included in creams and other personal care products.

The full study is published in the New Phytologist, an online academic journal.

The researchers were able to assemble a complete genome from a new cannabis variety and also examined several different cannabis varieties. They found that by breeding high-THC marijuana plants with lower-THC hemp varieties, breeders can develop new varieties that produce high levels of CBD. THC, or tetrahydrocannabinol, is the chemical in marijuana that gives a "high."

But according to co-author CJ Schwartz of Sunrise Genetics, this breeding feat “poses a challenge” — and big risk for farmers, according to study

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“The genes that allow for the production of CBD are also a bit ‘leaky,’” Schwartz said. “This can result in about 5% of the product ending up as THC instead of 100% CBD.”

Farmers who grow high-CBD varieties to maturity have a much higher risk of their crops going "hot," crossing the federal legal limit of 0.3% total THC.

“These high-CBD plants are genetically marijuana for the most part and they can’t be expected to meet the legal definition of industrial hemp in every situation,” said study co-author George Weiblen, a professor at the University of Minnesota.

“This means that CBD products — such as flowers, extracts and edibles — that are labeled ‘hemp’ could be incorrectly labeled and falsely branded. Fiber hemp and products made from hemp seeds, however, are drug-free.”

Weiblen and a team of researchers also developed a genetics test in late 2020 that can predict whether a cannabis plant will produce mostly CBD or THC molecules.