CANNABIS SEEDS - COLCHICINE, TRIPLOID, TETRAPLOID, POLYPLOID EXPLAINED
1. What exactly is polyploid cannabis?
Ok so before we get to polyploid cannabis or polyploid cannabis seeds, let's first talk about bananas.
The bananas we are used to finding in stores are polyploids. Specifically, they are triploids.
Why does this matter to cannabis or cannabis seeds I hear you say. Well it matters to cannabis and cannabis seeds because the characteristics for which we have the banana cultivars we have, are desirable characteristics that make the banana seedless and the trees that grow them, more efficient fruit producers than wild banana plants.
Wild banana plants are not polyploid - they are diploid. Wild banana plants have huge seeds and small bananas - where as triploid bananas are seedless and develop large fruits.
Banana cultivars in use today were all developed because the triploid plants are of better value commercially in terms of yield and profitability, but also for consumption. Imagine going to a shop and finding small bananas full of seeds in comparison to what we actually buy today.
This is why polyploidy is often used in agriculture, for many plants, like bananas, corn, watermelons amongst others. The main reasons are for uniformity, crop yield and crop quality.
In cannabis or with cannabis seeds, because of the restrictions of the last century, there is not enough available information about polyploidy or its impacts and applications. We will try to cover as much of this is as practically possible so that the layman can understand it.
In a normal cannabis plant, the genome is diploid, just like in human beings. What this means is that diploid organisms contain two sets of chromosomes in each cell. You might remember from school that chromosomes are the tiny little bits of nucleic acids in the cell nucleus that carry genetic information. They are like building blocks, in such that when combined they transfer the information they contain, during cell division, which itself is known as mitosis.
Most cannabis seeds are diploid by default, however there can be spontaneous mutants and we'll cover that later.
Nature has evolved plants and other organisms as diploids because diploids offer survival mechanisms and methods of long term organism viability through the copy paste method that we know as DNA.
When diploid organisms breed, one set of chromosomes from one parent, is combined with another set of chromosomes from the other parent. This results in diploid offspring where each cell has two sets of chromosomes - the combination derived from the parents. The possible expressions of a diploid organism are limited by those parental chromosomes.
When we talk about polyploids, we are talking about organisms that received more than one set of chromosomes from any parent.
For example, in cannabis which is diploid, when bred, the chromosomes present are from parent A which supplies 1 set, and parent B which supplies another set. Each set contains 10 chromosomes, so when recombined, making 20 chromosomes, namely two sets of 10 each, per cell of the progeny plant.
However, in polyploid cannabis seeds, one or more of the parents has passed down more than one set of chromosomes. A triploid plant passes 3 sets of 10 chromosomes. A tetraploid has 4 sets of 10 chromosomes and so forth and so on.
So, let's conclude this section with the understanding that polyploid cannabis is cannabis seeds produced where one of the parents had more than one set of chromosomes that were passed to the progeny cannabis seeds.
2. Why does polyploid cannabis have the potential to be better than diploid cannabis?
If we go back to the banana example in the previous section this is very easy to understand. The main potential is to have better quality cannabis flowers and high yielding cannabis seeds obviously, but there are also some other reasons.
Polyploid cannabis plants potentially can be stronger plants overall, sturdier, higher yielding and also potentially more drought tolerant than their diploid relatives. Polyploid cannabis plants can have more available genetic flexibility and hence a broader range of adaptability in comparison to diploids.
But more interestingly in the modern era, its because the available combinations of terpenes synthesized by the plant are exponentially increased through polyploid cannabis.
The other area of interest in cannabis polyploidy is in the retention of polyploid traits in certain parts of the plant but not others. In particular, this applies to flower structure and trichome density.
When it comes to flower structure in cannabis plants, the more available bracts, the higher the potential for trichome production.
On the surface of the bract, where different types of trichomes form, some trichomes secrete cannabinoids and terpenes. It's the density of these particular trichomes that could be improved in comparison with diploid cannabis, that polyploid cannabis seeds provide the opportunity for.
Another aspect of certain polyploids, for example triploids, is that they are mostly infertile. So if you grow cannabis outdoors, a field of triploid females from high quality triploid feminized cannabis seeds can never produce cannabis seeds in large quantities like their diploid relatives can.
Let's cover the main points before we move to the next section - in simple terms polyploid cannabis or polyploid cannabis seeds have the potential to produce larger, higher quality, higher yielding cannabis plants that have a far broader range of terpene expressions combined with potential for higher cannabinoid production. Polyploids also have application in cannabis because of higher infertility - this applies to triploids. Polyploids can have more drought and pest resistance than their diploid relatives.
3. How are polyploid cannabis strains made? How much colchicine for cannabis applications?
Polyploids rarely form as a result of mutation in nature. When they do occur, it may be for a brief period only and many if not most will "revert" to diploid as the genome corrects itself. For example sometimes cannabis seeds will sprout with 3 leaves at every node instead of the usual 2. This is a triploid trait. However, the majority of these will "revert" to 2 leaves per node as they approach preflower stage. In cannabis, a natural polyploid that grows to maturity is extremely rare.
Most cannabis polyploids are created by using mutagens.
The most well known mutagen that is used in agriculture overall for inducing polyploidy is a chemical called "colchicine".
Colchicine is typically prescribed for gout and is also available in tablets for agricultural use.
Colchicine requires careful handling during use and thoughtful disposal. Cochicine is a mutagenic poison and restricted chemical in most places.
It is NOT RECOMMENDED to use colchicine for these purposes unless you are a trained agricultural professional.
Producing polyploid cannabis involves some different methods which we will detail below.
a) Colchicine seed soak - cannabis seeds are soaked in a solution of between 0.25% to 0.5% colchicine. Seeds that do sprout are observed for polyploid traits and a separate set of seeds from the same batch should be used as a non treated control to ascertain the success of the treated group. The viability of the treated seeds is far lower than that of untreated seeds.
b) Sprouted seed soak - this is similar to the process described above however instead of soaking cannabis seeds in a solution of colchicine, but instead take seeds that have already shown a tap root and give them a quick dip in a solution of the same concentration. The seeds that continue on to grow into plants need to be assessed for polyploidy in comparision to a untreated control group.
c) Meristem treatment - this method involves a growing plant, where the meristem, apical or intercalary ( the tip at the branch nodes ), is treated with a solution of colchicine. For this type of treatment the colchicine concentration should be between .5% and 1% of the solution. This method is best used with clones because untreated clones can be used as the control to validate the differential in the treated clones. This treatment has to be done with a dropper bottle because colchicine is toxic, it should never be used with a spray bottle or delivered as a mist that can be breathed in by humans.
d) Clone dipping - somewhat similar to meristem treatment, this method involves taking a rooted clone and dipping the entire non root section into a colchicine solution. Similar to meristem treatment, the solution should be .5% to 1% colchicine. Untreated clones have to be used as the control to validate the effects of treated clones.
Typically, these treatments will deliver mostly tetraploid characteristics that are expressed in the surviving plants, depending on treatment method.
Tetraploids that survive and that are fertile, can then be crossed with diploids to produce triploid cannabis seeds, which have the infertility characteristic that many desire - triploid cannabis seeds capable only of producing high quality seedless cannabis flower or sinsemilla, which literally means "no seeds".
In some tetraploid specimens, only certain polyploid traits are expressed. For example, plants could express 4 leaves at every internode instead of the usual 2. Or they could express double or quadruple bract stacks, instead of usual one. Some specimens could express flowers in a fashion where every bract produces 2 sets of pistils ( 4 visible hairs instead of the usual 2 ). There could be up to quadruple the amount of trichome stalks, greatly improving the overall trichome density which in turn boosts both cannabinoid and terpene yield.
The breeders who are well versed in these techniques can then select and breed from these parents to make progeny that are true breeding for those traits going forward.
To summarize this section, we have covered the different methods of treatment with colchicine for cannabis seeds or cannabis plants and the types of results we could potentially expect, along with understanding that the grower needs to always have untreated specimens as controls to determine whether the treatment was successful or not.
4. Where do I get polyploid cannabis seeds?
Right now there aren't any specific sources of polyploid cannabis seeds as this is a new area for cannabis seeds. Unlike other plants, where methods and cultivar availability are well advanced, with regards to cannabis seeds, this area is a developing space where breeders particularly in the Americas are now working with polyploidy in cannabis.
Cannabis breeders are acutely aware of the benefits of polyploidy and it is probable that the industry will develop specific polyploid cultivars in the near future.