How do we know which cannabis strains carry polygenic or multi-allele dominance and in which phenotypes?
How do polygenic and multi-allele trats, as well as the lack of genomic data, specifically limit targeted cannabis breeding projects?
Without a genomics lab, observation and careful note taking. If you observe that a particular trait of interest is not following a predictable “discreet” frequency of expression in subsequent generations, then you may well assume the trait is polygenic. How you would then treat this trait depends on whether your plant numbers are sufficient enough to discern the potential expressions of this trait.
For practical purposes, I have never come across a breeder that is either expecting to be able to, much less putting to work, the ability to guarantee specific genotype stability in each seed. Meaning, it’s not realistic to expect to be able to breed a line so true that you could guarantee the exact height/potency/flowering time, etc. to the inch/%/day etc. You are dealing with a range of variation. It would be realistic to expect to produce a line of specific traits that express within a range of “acceptable” manifestation. So while I can’t say that every seed will result in a female finished at 63.4days at 2.36’ with 18.23% THC; I could achieve my goals to be able to say that this seed will finish around 60-67days, 2-2.5’, with 16-19%.
I can say I have this Afghan Skunk line that is short. I can’t tell you the exact height, but through selection and testing, when flipped at 1.5’ the progeny will finish between 2-2.5’. The deciding factor between one plant finishing at 2’ and another at 2.5’ may very well be polygenic, but the genotypes have been trimmed to be within this range of possibility, so I can treat the trait as discreet. My treating the trait as discreet isn’t ignoring the fact that it’s polygenic; it’s simply an adoption of a practically useful tool with the understanding that, as with most scientific models, this is an approximation.
At best, I could say that in a pack of seeds, you’ll find a short plant of high potency and quick maturation, but could not guarantee that every seed will express an exact phenotype.
Is the cannabis hermaphroditism trait polygenic, multi-allele, a combination, or caused by some other mechanism or combination of mechanisms? If something else, what?
I would speculate that all traits are polygenic. The question is to what extent is the trait dominated by variable contributing factors. Is the resulting spectrum of possibility such that it can be treated as discreet within a set range of acceptance? What of co-dominant contributions resulting in a “new” trait (
think red flower and white flower creating pink flowers)? I’d familiarize myself with the possibilities and allow the manifestation of these traits through observation guide which assumptions to accept for further work.
No two genotypes are the exact same, and I would have to assess each plant independent when it comes to questions of specific traits and how they express/breed.
Here is an example of a far better equipped group exploring this concept:
Even in a high-tech environment, the assumption of simple Mendelian inheritance is a useful model (
red). While the hermie trait is in fact a polygenic trait gaining it’s form through the contribution of many genetic affecters, the expression is discreet (
blue). Were I breeding plants that behaved exactly like this, my limited inheritance model (discreet) would still work, regardless of my ignorance of the far more intricate underlying polygenic nature. In essence, the polygenetic traits are irrelevant if the final expression takes on a discreet form.
Without having the cannabis genomic data or knowledge of its polygenic and multi-allele traits, how do you true breed?
This could be a long response, so I’ll limit it to the overall approach:
Assume a discreet model (
as long as the range of trait expression is within your acceptance) and take notes about your frequencies. Keep your traits limited, observe their frequency, compare to the Punnett predictions to “reverse engineer” the genotype. Then move forward with another trait. In short, you’d have to benchmark your plants at each step.
How does the science of epigenetics relate to breeding cannabis?
Epigenetics relates to the phenomena of transcendent genetic affects relating to functional groups (methylation, phosphorylation, etc.) attaching to DNA affecting transcription and gene expression.
Certain chemical functional group molecules can attach themselves to the DNA and histones (
proteins DNA wrap around). These attached groups can affect how the DNA is wrapped affectively “shutting off” certain gene expressions. These can come from environmental factors, stress by-products, chemical additives, etc. and affect the genetics in such a way as to alter their original potential expression.
I’ll use an analogy to simplify this. Let’s assume I have my favorite album on CD and I listen to it all the time. One day, I accidentally drop the CD on the floor and lightly scratch on part of the CD. Every time I play the CD, when the laser gets to this small scratch, the music skips. If I try to copy this CD or play it, I’ll forever have this skipped part of the music. Does this mean the album has been so destroyed that I couldn’t tell it’s still my favorite band? Nope, it just skips that little bit of the guitar solo on track #3.
The DNA is like the CD in that it contains all of the information I need to “replay” this set of info. If epigenetic factors “scratch” one segment of this info, I will now experience a small imperfection moving forward with genes being “lost” and will now affect any copies of the information being made in the future.
I would speculate that while the epigenetic alterations to genetic material could result in large observable changes in a population, they’d mostly take the form of very low-level disturbances. So I would be more apt to expect one vein pattern of one leaf blade to be slightly more fractal than otherwise expressed, more so than the plant now producing 27 blade leaves.
To the extent some claim cuts are experiencing “genetic drift” as they are kept in different environments for periods of time, I’d credit epigenetic factors. I don’t really buy the claim that a cut has taken on the exaggerated differences some claim as genetics are more resilient than a few years in different mother rooms could impress.
I am not aware of any specific procedural points to be aware of during cannabis breeding in order to avoid unwanted epigenetic factors playing a role. There are some genetic modifications you can introduce in order to induce minor/severe genetic manipulation. These techniques are widely used in agricultural breeding and involve purposeful mutations through chemical means in order to alter a plant’s genetics. I’ve played around with this idea but don’t post much about it as many have differing opinions and presuppositions about GMO breeding and don’t feel like having to get mired in thinly veiled political debates about stuff no one else is even doing. I don’t use it on any released work (
so don’t worry if you’re growing Schwaggy Seeds).
An example of this that many may be familiar with is GA3 used early to induce exaggerated growth rates. This technique is temporary and is regulated by the presence of the chemical stimulant. There are other methods of permanently altering the DNA of plants in order for the mutation to be heritable (I’ve messed with radioactive smoke detector material (Americium-241) to introduce limited ionizing radiation to plants), but is very hit/miss as far as at-home practical use. It’s something to be aware of, but I wouldn’t worry too much as I’m of the opinion that these issues at best dance on the periphery of genetic alterations.