What’s in a strain? Studies show that many strains aren’t unique

Remember the days when you had to hit up that neighborhood college student for pot? You took your chances taking whatever he had on hand: maybe good, maybe bad, maybe some really dry stuff on occasion.

Today, in the days of legal commerce, there are so many choices that retailers have actual menus so you know what is available and how they are different.

Well, turns out those menus might not be needed, and you may just have to take whatever you can get at the pot shop.

Researchers in Nevada recently released results from a study of medical marijuana samples. The study looked at approximately 2,600 samples of flower gathered in 2016 and 2017 that represented almost 400 strains.

When all the samples were analyzed, researchers discovered something surprising: despite all the clever and creative names to distinguish one strain from another, there were only about three distinct chemical varieties of cannabis.

Most of the cannabis available in the U.S. today is defined as hybrid due to factors like psychoactive and medicinal effects, plant type (combination of indica or sativa), appearance, taste and odor.

These varieties are commonly referred to as “strains.” In scientific vernacular though, strains are known as “chemovars” because the science community uses “strain” in relation to bacteria or viruses, not to describe plants.

For this study, published in the journal Cannabis and Cannabinoid Research in October 2020, researchers used a third-party testing laboratory to analyze both the terpene (natural aromatic oils that give cannabis varieties distinctive flavors like citrus, berry, mint, or pine) and cannabinoid (chemical compounds found in the cannabis plant in differing quantities) content of each sample.

According to the journal’s description of the study, the lab looked at the principal components that made up each sample in order to define “clusters” in data sets that represented both cannabinoids and terpenoids, cannabinoids only, or terpenoids only. There weren’t as many clusters as many expected:

“The number of predicted clusters was small: two clusters for cannabinoids and terpenoids combined, three clusters for cannabinoids only, and three clusters for terpenoids alone.”

For cannabinoids, 93% of the samples fell into one cluster, or had a very similar makeup. Except for the samples that were high in CBD, all samples contained high amounts of THC, an average of 22%, and very small amounts of other cannabinoids.

For terpenes, there were three distinct clusters, representing 59% myrcene (the most common terpene in cannabis that is responsible for the peppery, spicy, and balsam smell), 33% terpenine (a group of isomeric hydrocarbons that derives naturally from cannabis and other plant sources, including cardamom, marjoram, and oils of juniper and eucalyptus), and 8% limonene, the major component in the oil of citrus fruit peels.

How did this happen, when we have been led to believe we have so many options when it comes to legal marijuana?

“The vast majority of commercially-cultivated Cannabis plants are produced through cloning,” wrote study researchers. “Clonal propagation ensures that plants are genetically identical to the mother plant. In contrast to varieties propagated through seeds, requiring a lengthy process of backcrossing and inbreeding to achieve consistency, new chemovars can be created much faster by clonal propagation. New chemovars are constantly generated and enter the market, resulting in thousands of different breeder-reported names without any scientific naming convention.”

The lack of standardized, uniform cultivation practices leaves it up to growers to classify their product, then name it accordingly. Which isn’t an issue, until you consider that this can be confusing for medical patients who depend on identifications as well as potency data on the packaging.

“The potential for mislabeling of chemovars, inconsistent chemical profiles of marijuana products, and often limited testing data make it difficult or impossible for many patients to obtain a consistent chemical profile of the product,” states the report.

A separate study, documented in the Journal of Cannabis Research in June 2019, also showed that names don’t appear to mean much when it comes to marijuana. But the conclusion of this study is a little different: strains with the same names, purchased at different locations, are often not actually the same strain at all. This study took samples of 30 legal prominent cannabis strains from 20 dispensaries in Washington, Colorado and California.

A genotyping technique of sequencing, commonly used in plant genetic studies, was used to identify genetic groups. It came up with two distinct groups, and surprisingly, they did not correspond to sativa, indica or both.

For instance, two strains commonly known to be sativa-dominant, Durban Poison and Sour Diesel, would have been expected to belong to the same or close genotypes. But study results indicated they had contradicting genetic assignments.

Similarly, three other “similar” strains tested – Purple Haze, Pineapple Express and Tangerine – were thought to be 60/40 hybrids of sativa and indica. But they all were found to have differing makeups.

This study found that almost every same-name strain tested had at least one or more genetic outliers that were mismatched and did not have a similar or same genotype.

“Only four strains out of 30 had consistent genotype assignment and admixture,” wrote report authors Anna Schwabe and Mitchell McGlaughlin. “If you removed the 1-2 outliers, then 11-15 strains showed some consistency, genetic stability and relatedness.”

Study researchers do note that environmental factors like light and cloning over several years can put enough stress on cannabis plants to create differences across a single strain. But overall, they say that after removing outliers, only about half the strains had at least some genetic stability and relatedness.

So what does this mean for you when you go to your neighborhood cannabis retailer? It’s unclear, but in the future you may have fewer decisions to make when shopping.