It’s been said that a rose by any other name would smell as sweet, but that’s not always the case with cannabis.
Despite Shakespeare’s famous line from Romeo and Juliet, names and what we call things are important, especially with medical cannabis.
As a physician, I have always been skeptical of the labeling and consistency of individual drug-type strains that my patients choose from at the dispensaries. For medical cannabis to be a successful therapeutic; it is critical to have reliable and consistent properties within the strains or chemovars recommended to patients.
Aside from the wild names (such as “Sour Diesel,” “Purple Kush” or “Girl Scout Cookies”) these drug-type strains in many dispensaries are designated as Sativa-dominant, Indica-dominant or hybrid. This harks back to their ancestral origins; however, this is probably not valid anymore. While the distinction of these ancestral landraces may have originally been created by their native geographic regions with different climatic conditions, the thousands of years of man’s cultivation and dispersion  inadvertently caused natural selection, which ultimately mitigated many of these differences.
Additionally, the prohibition of cannabis over the last century has also exerted an underground cultivation selection pressure on these hybrid plants for years. Unlike regulated farming practices cultivating strains and varieties of legal plants (such as fruits or flowers) there is no official database for cannabis, leaving cannabis growers to create their own strains clandestinely in silos.
And in the U.S., despite increased legalization and decriminalization of cannabis, it is still considered a federally illegal plant, and there are still no standardized, uniform cultivation practices like those covered by the USDA’s Plant Variety Protection Act. This leaves it up to the states’ growers, who are still essentially cultivating strains on their own.
But in our modern era we have a scientific way to distinguish these differences in strains and cultivars with detailed genotyping, which allows us to address strain variability on the molecular level.
An excellent research paper by Anna Schwabe and Mitchell McGlaughlin, titled, “Genetic tools weed out misconceptions of strain reliability in Cannabis sativa: Implications for a budding industry” addresses this issue. The researchers used genotyping to examine different samples of various strains with the same nomenclature in the hopes of determining if there is any genotypic validity to the distinction of Sativa, Indica and Hybrid, as well as any uniformity within these specifically like-named strains.
Schwabe and McGlaughlin’s paper hypothesized that the genetic profiles from samples of plants designated as the same strain should have identical or highly similar genotypes despite coming from difference sources. They took samples of 30 legal, well-known cannabis strains from 20 different dispensaries in 3 states (Colorado, Washington and California) to answer 3 basic questions:
- Is there any genetic distinction that separates the common perception of Sativa, Indica or Hybrid types?
- Is there consistent genetic identity found within a strain variety obtained from different facilities and growers?
- Is there evidence of misidentification and or mislabeling?
They used a genotyping technique of sequencing that is commonly used in plant genetic studies looking for Single Sequence Repeats (SSRs), also called microsatellites. These markers are long, repetitive sequences of DNA, which sometimes are non-coding or not part of a gene. These microsatellites also have a high degree of mutations, making it easier to identify genetic diversity. But they can also be used to look at linkage and inheritance of gene families, as well as measuring and estimating levels of relatedness and kinship between genotypes. Essentially, they can define cultivar DNA fingerprints.
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They developed 10 de novo microsatellite markers using the previously sequenced genome of Purple Kush. The researchers also used the common online database of Wikileaf’s descriptions of the strain’s proportions of Sativa, Indica and hybrid to then look for validation of these proportions genetically.
Answering their first question, the study identified two distinct genetic groups. However, these did not correspond to the designations of Sativa, Indica or hybrid mixture.
For example, according to Wikileaf, 2 Sativa-dominant strains, Durban Poison (100% Sativa) and Sour Diesel (90% Sativa) which theoretically should have belonged to the same or very close genotypes in fact, had contradicting genetic assignments. They belonged to the two different genetic groups, despite Wikileaf’s assignment of Sativa dominant. Additionally, an example of 3 other strains, Purple Haze, Pineapple Express and Tangerine which were all supposed to be 60/40 hybrids of Sativa and Indica were found to have differing admixtures both within the same name strains themselves and also when comparing them to each other.
This study shows us that the designation of Sativa, Indica or Hybrid proportions has no true genotypic validity today.
But is there a consistent genetic identity within strains themselves from differing facilities and states?
What the study found was that almost every same-name strain tested had at least 1 or more genetic outliers that were mismatched and in fact did not have a similar or the same genotype. Only 4 strains out of 30 had consistent genotype assignment and admixture, and, if you removed the 1-2 outliers, then 11-15 strains showed some consistency, genetic stability and relatedness.
For example, looking at the 9 samples of Blue Dream, which is purported as a clone-only strain, when the single outlier was removed all the rest had high degrees of first order relatedness. However, this is still more variation than would be expected from a clone-only strain, which one would think should be genetically identical.
This brings up the issue of variability while creating botanical medications: other factors are at play even with cloning.
Expression of genes may differ with environmental factors such as light and even multiple years of cloning that may stress plants enough to create these differences. But, overall, when removing outliers, around half of the strains had at least some genetic stability and relatedness.
This brings us to the last question: Is there evidence of misidentification or mislabeling?
The authors say that, while it may likely be unintentional, there are many points in the chain from growers to processors to dispensaries that may have misidentified or mislabeled their product since the majority of operations do not use genetic tools and only use phenotypic properties. Trying to use characteristics such as smell, color, or bud size, makes correctly identifying strains extremely difficult considering the number of strains out there and the new strains constantly being developed
One of the limitations of this paper was the small sample size. First, the number of strains used was only 30, compared to by some accounts, reports of 100-700 different named cannabis strains.  Additionally, even within those named strains used, some of the tested strains came from only 2 different facilities so again there was a small sample size examined. Also, their technique of using the microsatellites approach is not the only way to genetically test cannabis.
This is a very targeted way to look at genotype and, as discussed earlier, these base-pairs are mutation prone areas which can highlight their genetic diversity a bit more. Perhaps future studies could look more broadly at the whole genome of all of these strains. While more tedious and time consuming, it might be a better way to highlight important genetic similarities such as the cannabinoid synthesis loci.  The specific cannabinoid, terpenoid and flavonoid profiles are the most important traits in these medicinal plants.
In conclusion, studies like this are very important. And going forward, as cultivation techniques become a much larger and better regulated businesses, albeit still only on the local state levels, genetic genotyping should be required as a necessary and critical tool to help ensure therapeutic consistency, for medical cannabis at the very least. Future research to help identify chemotypes genetically and more accurately in different strains is tantamount.
Physicians and patients alike have a hard time taking a therapeutic regime seriously with names like, “Alaskan Thunder Fuck” or “Green Crack.” To further legitimize this field, I personally hope to see in the future nomenclature for medical cannabis changed.
Dr. Leigh Vinocur is a board certified emergency physician, who also has a cannabis consulting practice for patients and industry. She is a member of the Society of Cannabis Clinicians. And in the inaugural class for the first Masters of Science in the country in Cannabis Science and Therapeutics at the University of Maryland School of Pharmacy.
This blog is not written by Hearst. The authors are solely responsible for the content.
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