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Unravelling the Genetic Map of Cannabis: The Road to Designer Strains

By Jack Rudd

, Leo Bear-McGuinness

Published: Nov 27, 2018   
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A new ‘genetic map of cannabis’ could help create tailor-made cannabis plants that only express desired genes.

The first-of-its-kind map is made up of the nearly 25,000 genes found in cannabis’ 10 chromosomes from three different cultivars: hemp, a high-CBDA strain and a high-THCA strain (these are the genes which code for CBD and THC respectively).

As a powerful new resource for cannabis companies, the hope is that the map will go on to inform growers of the locations of desired genes and, therefore, help then in breeding bespoke varieties.

Despite several other attempts to sequence the cannabis genome, the map is also the first of its kind to show the lost ancestral links between different cannabis cultivars.

In a paper published in BioRxiv – that is still in pre-print and awaiting peer-review – the map’s researchers reveal that high-CBD cannabis plants appear to have been created when hemp-like and marijuana-type cannabis cultivars were hybridized.

The research was conducted by some of the leading genetic institutions of America, including the Craig Venter Institute, Sunrise Genetics Inc. and the universities of Harvard and Minnesota.

Cannabis Genetics 

From its leaves to its roots, its terpenes to its THC, every part of a cannabis plant starts with its instruction manual, the genetic code.

As the cannabis industry continues to grow worldwide, access to this instruction manual has become very valuable. So much so that the new genetic map of cannabis may become a highly prized resource for growers.

“With the genomic map, we can now more precisely identify the genetic differences among these three types to breed tailored cannabis strains,” CJ Schwartz, CEO of Sunrise Genetics, one of the founding partners in the genetic map project.

Speaking to Marijuana Venture in July, Schwartz claimed that the map “will allow all cannabis researchers worldwide to coordinate their data for finding important genes for numerous traits.”

“The impact on the community and the sophistication of cannabis research and development will be substantially changed, bringing cannabis to the same level as other economically lucrative crops.”

According to Schwartz, the genetic map will help transform cannabis breeding into a more scientific and tailored process. If a grower wished to produce a strain (cultivar) with higher levels of THC, it would be possible to find the most stable THCAS gene in their plant and track its increase through generations.

Plus, in Schwartz’s own words, “DNA evidence can also be used to protect cultivators and their favorite strain so that no one else can patent the strain and prevent/sue somebody for growing it.”

Whether the genetic map will become an indispensable key to the cannabis industry’s future remains to be seen. But what is clear, is what it reveals about cannabis’ past.

The Cannabis Genetics Map

It’s well known that cannabis cultivars are divided into two major classes: those with high CBD and low THC contents, and those with the reversed ratio.

According to findings in the genetic map, it’s this divergence in cannabinoid content that marks the historic, genetic differences between the two groups.

To gather their findings, the researchers had to first determine which genes they were going to look for and differentiate. They chose two, the ones that code for the two most famous and questioned cannabinoids, the THCA and CBDA synthase genes.

To search for the history of these two genes, the group sequenced 100 whole genomes of different cannabis varieties, from skunk to hemp to hybrids. Together, these sequences made up the unique genetic map of the cannabis plant in all its variety.

To find their way around, the team searched for the genes’ loci – positions on chromosomes that mark out the location of certain genes.

Located along the ominously titled chromosome 9, the group found not 1 but 13 different cannabinoid synthase genes amongst the sampled varieties. As this large number of copies would not normally be expected of such an important gene, it’s likely that there were distinct evolutionary differences in the cultivars’ history.

Indeed, their results suggested a strong, divergent history of cannabis plants, one where independent breeding paths took the two cultivars in different directions, with little gene flow between domesticated populations.

This wide variance is perhaps indicative of cannabis’ historically illegal status.

Under harsh punishments for producing and selling psychoactive substances, hemp plants were bred to have as low a THC count as possible, while over in the clandestine operations, the opposite was true in order to match the illegal demand for mind-altering drugs. In essence, federal prohibition acted upon cannabis evolution much like harsh environmental conditions, a new predator in the ecosystem or any other strong evolutionary pressure.

But now, as prohibition is slowly repealed around the world and medicinal use encouraged, this guiding federal pressure is fading. And in its place, hundreds of different selective forces, each trying to turn one cannabis batch into its own unique product. From terpene-rich to THC-heavy, cannabinoid ratios are not just scientific data anymore, they are product labels.

And maybe, with the right understanding and application, the new genetic map of cannabis can help the industry in creating the next wave of bespoke merchandise.

Jack Rudd

Editorial Director, Analytical Cannabis

Jack has been working in science publishing since 2015 and has been the editorial lead of Analytical Cannabis since its launch in early 2017. He holds a 1st class Bachlor's in Biological Sciences from Essex University, where he received the distinguished Eliahou Dangoor scholarship for his work. He is also a member of ASTM Committee D37 on cannabis and attends a number of annual international cannabis science conferences. Prior to the launch of Analytical Cannabis, Jack worked in editorial for our parent publication, Technology Networks, where he focused on covering developments in cancer research, genomics, and informatics.

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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