testing cannabis plants for thc or cbd
testing cannabis plants for thc or cbd

Revolutionary New Test Predicts if Cannabis Plants Will Be High in THC or CBD

Problems with testing hemp over 0.3% THC could be a thing of the past!

Posted by:
DanaSmith on Wednesday Nov 25, 2020

Revolutionary New Test Predicts If Cannabis Plants Will Be Rich In THC or CBD

cannabis plant testing for cbd or thc

When the 2018 Farm Bill was enacted, hemp became legal in the United States.


Though it seems like CBD consumers would benefit the most from this move, Congress actually wanted hemp farmers to benefit from the massive demand for CBD, which naturally occurs in hemp. It’s no surprise that CBD infused products have been popping up almost everywhere these days, whether it’s in beverages, chocolates, body lotions, and so much more.


However, the truth is that the law is so much trickier than that. It may look like a pro-CBD bill on the surface, but the US Department of Agriculture stated that hemp should contain under 0.3% THC at the most, or else farmers could risk their crops being destroyed and they would also have to pay for state-sanctioned tests to determine its THC levels. Unfortunately, for too many farmers, failed tests have become too common and they have lost so much potential income from this.


“Hot hemp” refers to hemp crops that ended up having higher than the 0.3% desired THC level. And it’s far too difficult for farmers to determine just how much THC will be in the next harvest. “The biggest factor contributing to the issue of hot hemp is probably the genetics that growers are sourcing,” explains Bob Pearce, Ph.D. agronomy professor at the University of Kentucky. “Cultivars that produce predominantly CBD also produce small amounts of THC, typically in a pretty consistent ratio for that cultivar. So, as CBD increases so does THC. Then you throw in environmental stress and management on top of a marginally compliant cultivar, and you start to see problems with hot hemp,” he tells Hemp Grower.


Well, there’s finally a solution.


Revolutionary Genetics Test


Researchers from the University of Minnesota have come up with a revolutionary genetics test that can tell when a cannabis plant will have higher THC or CBD molecules. This test may just be the answer to hemp farmers’ prayers.


“We validated a simple genetic test that can predict whether a plant will produce mostly the CBD or THC molecule, using a variety of Cannabis sativa plants,” explains George Weiblen, a professor at the College of Biological Sciences as well as the Bell Museum’s Science Director and Curator of Plants.

To come up with the results, the researchers analyzed 3 types of cannabis plants sourced from industrial hemp growers, as well as ditch weed. They also studied cannabis samples obtained from the National Institute on Drug Abuse. They then studied the genetic markers specifically THC:CBD, then checked to see if the genetics were a reliable indicator of the ratio. It is the level of THC that helps them understand if the plant is actually cannabis or hemp, though the researchers do say that a THC-based definition doesn’t always match its biology. For this reason they suggested studying the ratio of THC to CBD.


They found that ditch weed that had both CBD and THC plants, which was a surprise. According to Weiblen, locating high-THC plants among ditch weed is a rarity although most cannabis users would have no use for them considering its low THC levels. They also found that some seeds reflected impurities; some were 100% CBD while others had too much THC to be considered legitimate industrial hemp. This is why Weiblen expressed skepticism of CBD products claiming to be 100% industrial hemp.


“We hope this new test can assist in new seed certification for the hemp industry,” he says. “For hemp to take off in Minnesota and elsewhere, there must be ways to assure growers they won’t have to destroy their crops at the end of the season.”


Genetics Are Responsible For Hot Hemp


Another study whose results were published earlier this year validate that it’s indeed genetics and not field conditions that result in hot hemp. Researchers from Cornell have proven that genetics and not stress response to cultivation conditions cause it, which is what popular belief currently says.


“Often that issue of going hot has been blamed on environment,” explains senior author Larry Smart, who also happens to be a professor for horticulture in the School of Integrative Plant Science. “People thought there was something about how the farmer grew the plant, something about the soil, the weather got too hot, his field was droughted, something went wrong with the growing conditions,” he says. “But our evidence from this paper is that fields go hot because of genetics, not because of environmental conditions.”


Smart and the team of researchers carried out field trials in 2 locations: Ithaca and Geneva, both in New York. They studied chemistry and genetics of 217 hemp plants. The two locations had varying growing locations, and they found that it didn’t have any significant impact on which chemicals the plants produced. However, when they checked the CBD and THC content of the plants and compared it to their genetics, they discovered a high correlation between genes and the chemicals produced.


“The molecular assays developed in this paper provide useful tools in breeding hemp,” says Jacob Toth, the paper’s first author, who is also a doctoral student for Smart. “To keep THC levels low, ensuring a lack of THC-producing genes will be important for the development of future compliant cultivars. Molecular testing is also much quicker and less expensive than current methods, and it can be done on seedlings instead of mature plants.”


The Cornell researchers hope that their findings will help reduce the occurrence of hot hemp by providing plant breeders with genetic markers that are easy to use, and can be utilized on seedlings as well as plants that are both male and female. The researchers were also successfully able to develop genetic markers to help breeders determine the sex of hemp plants before they flower. “This technology, at this point, too expensive for farmers to use on an entire field, but it will be very useful for breeders who want to separate males and females early on to better control cross-pollination,” Smart explains.






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