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Study: “Hot Hemp” Just A Matter Of Genetics

A new study has found hemp that goes “hot” – over legally permitted THC levels – is likely just down to genetics rather than environmental stressors also playing a role.

Most jurisdictions around the world have set levels for how high THC can be in cannabis before it is no longer legally considered hemp and it becomes marijuana. For farmers, this is a very big deal. A crop that goes over whatever level is likely to be destroyed and the farmer may face legal action.

Hemp farmers seek strains that produce crops coming under the maximum permitted THC level, but this doesn’t always work out. One of the factors believed to push a crop above are environmental stressors such as extreme heat.

However, a study carried out by the USA’s Cornell University hasn’t found any evidence that stress on hemp plants increases THC concentrations, or ratios of CBD to THC – which is another balancing act farmers need to contend with.

Five stress treatments were applied to three genetically unrelated high-CBD hemp cultivars. The treatments were:

  • flood conditions
  • exposure to a plant growth regulator
  • powdery mildew
  • herbicide
  • physical wounding.

THC and CBD content was tested over a four-week period when the flowers matured. Except for the plants treated with herbicide (which were nearly dead), the expected ratio of CBD to THC was produced

“What we found over the weeks that we were sampling, the amounts of CBD and THC went up proportionately in all of these different cultivars for all of these different stresses,” said study lead author Jacob Toth.

The researchers acknowledge a number of limitations in their study, include not testing for stresses that are typical of growing areas other than the northeast US climate, such as drought, extreme heat, or high salinity.

The Cornell study, carried out by researchers from the horticulture section of the School of Integrative Plant Science in the College of Agriculture and Life Sciences, has been published in the journal Global Change Biology-Bioenergy and can be viewed in full here.

Terry Lassitenaz
Terry Lassitenaz writes exclusively for Hemp Gazette and has done so since the site launched in 2015. He has a special interest in the political arena relating to medical cannabis, particularly in Australia, and addressing the many myths surrounding this incredibly useful plant. You can contact Terry here.

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