Almost a year ago I wrote “Cannabis: The Dumb Plant”, which was a simplistic look at why cannabis is different from conventional crops we know and love. In this article I’d like to delve a little deeper into what gives rise to variation within cannabis and how we can breed consistency into the phenotypes we desire.
First off, what is a cultivar? A cultivar is a conserved set of traits within a species. Broccoli is a cultivar ofBrassica oleracea, if I plant 100 Brassica oleracea seeds from the broccoli variety, all of the seeds will grow into what we know as broccoli. Cannabis is famous for not having stable traits in seeds produced from the same plant, we haven’t put cannabis through the same steps as we’ve put Brassica oleacea varieties through to get those consistent traits. Licenced producers have a library of plants with unstable traits that must be propagated though cuttings to keep those traits in the cannabis they produce. If they seeded their plants and planted the seeds, they’d produce 100 plants with different traits using seeds from the same plant. Why?
To answer why we can go back to Brassica oleracea. Those 100 broccoli seeds have a known lineage of conserved desired traits, crossing it with itself with produce those same traits. But what if I crossed the broccoli variety with the kale variety? Will my plants look more like broccoli, kale, or something new? We don’t know until we try.
A genome encodes for all the possible sets of instructions a species can use to give rise to variation. Instructions, or variants of the instructions, the plant uses as it develops defines the traits we see in a given environment. What set of instructions the plant uses depends on its parents. Cross broccoli with broccoli and you’ll produce broccoli, cross broccoli and kale and you get many plants with unique traits as the individual offspring inherit different preferences for instructions on the same genome based on their patents different preferences.
Cannabis follows the same principles, but the lack recorded lineages for each known strain makes it difficult to understand how a given trait we see can be stabilized. The manifestation of unique terpenes (smell), anthocyanins (part of colour), cannabinoid (effect) profiles, fungal resistance, cold-tolerance and drought-tolerance are more complex than single traits being inherited as Gregor Mendel observed. Breeding your favorite strain to produce the traits you love it for consistently from seed may take hundreds of crosses, self-crosses and back-crosses. Breeding is a numbers game, the more plants you screen in a generation the faster you’ll stabilize the set of traits you’re looking for. Breeding will become an essential component to the cannabis industry, as it currently is with every agriculturally relevant plant.
Phenotypic plasticity is the other factor that must be taken into account in breeding programs. Plants need to adapt to their surrounding since they can’t move to a better environment. If a specific trait is only seen when the plant is grown under certain conditions at a point in its life cycle, the breeder must know and try to account for those conditions to select for the desired trait. The more information we have the better we can design breeding programs, with cannabis the information is few and far between (and often not publicly available).
*‘Strain’ is being used in the commonly known sense in this industry to denote phenotypically unstable cannabis varieties.