Do plants have "strains"?
It has been published in several peer-reviewed papers that the term "strain" is inappropriate to apply to plants and is best reserved for micro-organisms. But is this true? The answer is...complicated...
While it is true, as we mention in the 2nd edition of the Curious About Cannabis book, that "strain" is NOT a taxonomical rank for plants, it is not actually true that there is absolutely no such thing as a botanical strain...technically. In our book we never actually said that there was no such thing as a botanical strain, but we did state the following:
"In botany and botanical taxonomy, there is no category called "strain" like there is in microbiology. For instance, there are various strains of the flu, or of E. coli. But this level of classification does not exist for plants..."
While technically true, "strain" is not a formal level of taxonomical classification for plants, this is worth expanding upon.
The controversy over whether there are true botanical strains or not relates, as it often does, to definitions...
What is a strain?
Just as in Cannabis taxonomy (and all of biological taxonomy) there is disagreement between biologists, ecologists, and geneticists regarding the technical definition of a "species", there is very similar disagreement about what constitutes a "strain."
The most common definition of "strain" that is employed in biology relates to a definition found in an early microbiology textbook from the early 1980s, which reads:
"A strain is made up of the descendants of a single isolation in pure culture and usually is made up of a succession of cultures ultimately derived from an initial single colony." (Dijkshoorn et al, 2000; Staley and Krieg, 1984)
However the word "strain" has been used in biology for much longer. You can even find published papers from as far back as 1930 or beyond using the term, but in ambiguous ways. (Nagai and Haba, 1930)
Hunting for a Botanical Strain Definition...
Throughout my college studies and in my professional life as a biologist, I never learned about botanical strains. Of course we learned about strains of viruses, bacteria, and fungi - but never in the context of plants or animals. In thinking about this issue I went back and looked through my various botany and biology textbooks to hunt for the term "strain" in a glossary to see how to properly apply it - but I could not find the term anywhere. Now, that has nothing to do with whether botanical strains are real - because as we know, there are all sorts of things that do not get taught in schools that are real (like the endocannabinoid system). However, the concept of strains, as I just pointed out, is not nearly as new a concept as something like endocannabinoids or the endocannabinoid system, and the fact that the concept of a botanical strain never arose in any of my biology or botany education actually says a lot. Had I been studying to be a geneticist, though, I may have learned about this issue sooner. The concept of "botanical strains" only really began to become more accepted and understood as genomic science has progressed and the genetic modification of organisms has become more widespread.
Stemming from that old definition of "strain" that I indicated above, many biologists may define a "strain" of something more broadly as an organism that has been artificially selected, usually in culture, to isolate a particular set of genetics. This is precisely why the term "strain" is most commonly used in microbiology. It is easy to demonstrate unique strains of bacteria or fungi because they are easily cultured, grown out, and replicated in controlled environments. Plus it is easier to study the genetics of micro-organisms and demonstrate this concept of "genetic isolation" that most biologists agree is critical to the concept of "strain."
What use is "strain"?
Extending the term "strain" to plants and other organisms is much trickier - and many argue that using the term "strain" to talk about other organisms is inappropriate because its meaning is so muddy. This would be the camp that I fall into - and this is my personal bias. For the vast majority of plants in existence, including the vast majority of domesticated crops, the term "strain" is usually extraneous and confusing.
But there are many horticulturists that use the term "strain" very loosely, often synonymously with "variety", "cultivar", or "cultigen". There is also an entire camp of scientists that choose to define "strain" as simply the progeny of an organism that has unique genetic characteristics from its parents. However, it is easy to see that this is a far departure from the traditional definition of "strain" and heavily dilutes the concept altogether. If that's all a strain is - then how is it different from a "cultivar" or a "cultigen"? In this context, it does not seem like it is different at all. So why use the word "strain"? Habit?
It is important to understand that when the term "strain" is used in this way, it is not as much a technical or scientific use of the word - and it certainly has nothing to do with taxonomy or formal classification. Instead it is more or less a shorthand way of communicating that an organism is a unique variety of its species in some way (sound familiar?).
There is also a debate among biologists over whether the term "strain" can be applied to an organism that has been "isolated" through "natural" settings like conventional breeding. This is because of the fact that the term "strain" hinges on this idea of defined genetic isolation. If a plant is not tissue cultured, it is destined to stray from the genetics of its host parent through propagation. Even cloning via cuttings results in some genetic drift from the parent, however small.
Botanical Strains in Action
However there are some modern examples where the term "strain" does appropriately describe certain varieties of plants in a technical sense. This primarily applies to highly genetically modified and intensely studied agricultural crops, like rice or wheat. This usually applies when particular genes, which can be measured, are inserted or deleted from a plant to produce a variety that would otherwise not exist in nature. This involves not just genetically modifying the plant but also culturing the plant to ensure that progenies are consistent to that "strain." This is one reason why a unique botanical strain may be modified so that it does not produce viable offspring, which helps ensure that plants grown under the label of a specific "strain" name will stay true to the characteristics of that "strain."
When you see the word "strain" used in the context of botany, it is almost always in the context of genetic modification of crops like rice or wheat. However, the term "strain" could be applied to Cannabis with the appropriate level of genetic testing and culturing to maintain the integrity of the "strain" - and in fact we will assuredly see true Cannabis strains emerge as more and more geneticists work with breeders to develop novel lines of plants that can be patented.
Look for Yourself
To reiterate my primary point here, I invite you to go to scholar.google.com and do a search for "botanical strain". You will find that you get approximately a dozen results, with only one or two peer-reviewed articles that use this phrase. If you want to do even greater diligence, search for "strain of plant" and peruse the ~500 articles that return and search for an article that refers to the concept of "strain" in association with a plant. For the most part, you will find very very few, and those that you do find will almost certainly be associated with genetic research.
So, do botanical strains exist? Sure. Are they common? NO. Are Cannabis "strains" actually strains? For the most part (because who knows what could be out there that is less known), NO. But true Cannabis strains will be coming following more widespread legalization across the world.
So the take away here is:
1. Botanical strains do exist, though they are very uncommon
2. Biologists and geneticists do not agree on how to appropriately use the term "strain" in the context of plants or other organisms beyond micro-organisms
3. Biologists, geneticists, and horticulturists often use the term "strain" colloquially in a non-technical manner, which can make the issue difficult to tease apart
4. Currently there are no (or - to provide benefit of the doubt - very very few) Cannabis varieties that could be proved to meet most accepted technical definitions of a "strain"
5. As genetic tools are applied to the Cannabis plant in the future, there WILL be more and more true strains produced - but they will not be the same as what we commonly think of as cultivated varieties of Cannabis which we call "strains" today.
6. I advocate for doing away with the word "strain" in botany, except in these rare use cases involving genetic modification and true botanical culturing, because "strain" is a loaded and almost always extraneous term. The terms "cultivar" or "cultigen" are better terms to use to describe unique plant varieties that have emerged due to artificial selection (human breeding).
A Note on "Cultivars": I have gotten into respectful disagreements with colleagues of mine that feel that a variety of a plant, like Cannabis, can only achieve "cultivar" status if an authority figure like the International Code of Nomenclature for Cultivated Plants (ICNCP) approves the designation. There is an argument that goes something like this:
1. The ICNCP controls what can be a cultivar
2. The ICNCP has not approved commercial Cannabis varieties as cultivars.
3. Thus commercial Cannabis varieties are not cultivars.
4. Thus, the next best way to describe them is to use the word "strain."
To be very technical, when the ICNCP approves a cultivar, the plant is given the categorization as a "cultivar" and is usually placed within a "group" that contains highly similar cultivars. They do not technically define what is and is not a cultivar, per se, but they define how cultivars are recognized in international horticultural commerce.
I reject the argument outline above for several reasons. One simple reason is - why does the ICNCP's non-acknowledgment of commercial Cannabis varieties mean that the term "strain" is okay to use? Why not "cultigen"? But I have even more fundamental objections to this argument.
While it is extremely valuable to have a central authority that helps define terms and ensure that horticultural industries are using terms consistently for the sake of good communication within the industry - this does not mean that the only definition of the term "cultivar" relates to how the term is used under an authority like the ICNCP. In the simplest term, a cultivar is simply a plant variety that has been produced through selective breeding practices and that is stable enough that it can be cultivated repeatedly and maintain its defining characteristics. You would be hard pressed to find a botanist or horticulturist that disagrees with this definition in its basic sense. So by this definition, all varieties of Cannabis are "cultivars", whether they are formally recognized in commerce or not. But as Cannabis legalization spreads across the world and the plant enters the larger agricultural and horticultural industries, it will be up to the ICNCP to decide how to group those cultivars (many "cultivars" of Cannabis would group together and be largely indistinguishable). But we are not quite there, yet.
At any rate, I hope this rambling has been useful to some of you that may have wanted to explore this issue of "botanical strains" more deeply. I'm sure that the issue is far from settled and we may have to revisit the issue again as general consensus within scientific communities changes.
Stay curious and take it easy,
Dijkshoorn L, Ursing BM, Ursing JB. Strain, clone and species: comments on three concepts of bacteriology. J. Med. Microbiol. 2000. Vol. 49. 397-401.
Nagai I, Haba S. On, the inheritance of variegation disease in a strain of Rice plant. Japanese Journal of Genetics. 1930. Vol. 5. 140-144.
Staley JR, Krieg NR. Classification of procaryote organisms: an overview. In: Krieg NR, Hold JG (eds) Bergey's Manual of systematic bacteriology. Vol 1. Baltimore, Williams and Wilkins. 1984. 1-4
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