Research shows that, genetically, high CBD 'hemp' plants are mostly marijuana
After assembling a genome complete from a new breed of cannabis, researchers at the University of Minnesota and Sunrise Genetics have found that high-CBD "hemp" plants have a genome that is mostly marijuana (THC). Published in the journal New phytologist, researchers found that plants with high levels of CBD inherit around 90% of their genes from psychedelic-type cannabis and the rest from hemp.
New study on cannabis genomics
Traditionally, cannabis plants are divided into two varieties : a type cultivated for its psychoactive properties (i.e. marijuana) and a type of hemp used to make industrial products like fiber. THC and CBD are the main cannabinoids and are present in both types (marijuana and hemp).
Researchers examined and assembled a complete genome from a new variety of hemp and also examined several different varieties of cannabis. They found that by crossing high THC marijuana plants with low THC varieties of hemp, breeders can develop new strains that produce high levels of CBD.
“Over the past decade, we have seen an increase in demand for CBD and we wanted to better understand how plant breeders have created plants with high CBD content to meet the growing demand,” said the co- author of the study George weiblen , who is a professor at the College of Biological Sciences (CBS) and the scientific director of Bell Museum .
But this breeding feat "is a challenge" and a great risk for farmers, according to study co-author CjSchwartz of Sunrise Genetics. Indeed the genes that allow the production of CBD are a bit "elusive", said Schartz in a statement. This can result in around 5% of the product ending up as THC instead of 1% CBD.
Researchers say this means that when plants with high CBD content are grown to full maturity, farmers interested in producing hemp for CBD run the risk of their harvest exceeding the federal legal limit of 0,3. % THC.
"These high CBD plants are mostly genetic marijuana and cannot be expected to meet the legal definition of industrial hemp in all situations," said the co-author of study, George Weiblen, 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 marked. Hemp fiber and products made from hemp seeds, however, are THC-free.
The full study is published in the New phytologist online. Weiblen and a team of researchers also developed at the end of 2020 a genetic test that can predict whether a cannabis plant will primarily produce CBD or THC molecules.
● To summarize in this study, the demand for cannabidiol (CBD) has encouraged cultivars producing unprecedented amounts of CBD. We investigated the ancestry of a new cultivar and cannabinoid synthase genes in relation to cannabinoid inheritance.
● A nanopore-based construct anchored to a high-resolution linker map provided a chromosome-resolved genome for CBDRx, a potent CBD-like cultivar. We measured cannabinoid synthase expression by cDNA sequencing and performed population genetic analysis of various cannabis accessions of. Quantitative mapping of cannabinoid trait loci in a hemp x marijuana segregating population was also performed.
● Cannabinoid synthase paralogs are arranged in tandem arrays embedded in long end-repeat retrotransposons (LTR-RT) on chromosome 7. Although CBDRx is predominantly of marijuana ancestry, the genome has acid. cannabidiolic synthase ( CBDAS ) introgressed from hemp and lacks a tetrahydrocannabinolic acid synthase sequence ( THCAS ). Three additional genomes, one of which is complete, THCAS have confirmed this genomic structure. Only cannabidiolic acid synthase ( CBDAS ) was expressed in the type CBD cannabis , while the CBDAS and THCAS all were two expressed in a cultivar with a THC: CBD intermediate ratio.
● Although variation between cannabinoid synthase loci may affect the THC: CBD ratio, variability among cultivars in overall cannabinoid content (potency) was also associated with other chromosomes.