Improving Your Cannabis Yields Via Genetics: A Tutorial

Generally speaking, people try to crossbreed related species because the resulting offspring benefits from what is known as “Hybrid Vigor.⁽⁷⁾” Of relevance to our concerns, however, are the species of Cannabis. There are 3 known species of Cannabis today:

Each species has different characteristics. When comparing them, it’s important to note several factors.

1. Size: C. Sativa grows to be the tallest of the three. C. ruderalis is the smallest. ⁽¹¹⁾
2. Leaf distribution: C. indica’s leaves grow densely-packed, while both C. sativa’s and C. ruderalis’ are more spread out. ⁽¹¹⁾
3. Ratio of THC to CBD content: C. indica generally has the highest THC to CBD ratio ⁽¹²⁾, whereas C. ruderalis has the lowest THC to CBD ratio (not much THC, but plenty of CBD). ⁽⁸⁾
4. Resistance to stressors: C. ruderalis is significantly more resistant to disease and pests than the other two species. ⁽¹⁵⁾
5. Variation within species: C. Sativa has been cultivated the longest by people, and thus has the most “breeds.” However, because C. ruderalis is closest to a “wild” cannabis plant, it likely has a significant amount of genetic diversity locked away, waiting to be discovered, in the same way that all dog breeds came from gray wolves. ⁽¹⁶⁾
6. Other differences: C. Ruderalis does not depend on light cycles for flowering. Instead, it flowers based on the age of the plant, termed as “autoflowering.” ^(13)(14)

[/cs_text][x_accordion][x_accordion_item title=”Crossbreeding (Additional Information and Ideas)” open=”false”]Generally speaking, crossbreeding different species either tends to not work due to pre-zygotic isolation, or tends to result in sterile or weak offspring, known as post-zygotic isolation.

Luckily, thanks to the evolution of the Cannabis family, all 3 species can produce healthy hybrids. ⁽⁹⁾ Unfortunately, there is a surprising lack of literature on the fertility of cannabis hybrids, likely due to the legality issue — major universities and research institutions do not want to risk losing funding or legal action.

This also means there is room to explore new breeds, including back-crosses, where you could theoretically have a 75/25% hybrid or other dilutions beyond 50/50.

If you really wanted to try some theoretical experimentation, you could try hybridization with other commercial crops. Corn (or maize) would be one crop to try, owing to an identical number of chromosomes. Looking elsewhere in the family of Cannabaceae, hops (used in beer, belong to genus Humulus) are a potential candidate for hybridization as well. [/x_accordion_item][/x_accordion][cs_text]Hybridization often tends to lead to infertility in the resulting offspring. While this problem cannot be solved in animals, it can be corrected in plants by inducing polyploidy, which we will cover in the next section.[/cs_text][x_gap size=”30px”][/cs_column][/cs_row][/cs_section][cs_section id=”2″ parallax=”false” style=”margin: 0px;padding: 0px 0px 10px;”][cs_row inner_container=”false” marginless_columns=”false” style=”margin: 0px auto;padding: 0px;”][cs_column fade=”false” fade_animation=”in” fade_animation_offset=”45px” fade_duration=”750″ type=”1/1″ style=”padding: 0px 0px 10px;”][x_line id=”3″ style=”border-top-width: 1px;”][x_custom_headline level=”h3″ accent=”false” id=”3″ class=”cs-ta-center”]Polyploidy[/x_custom_headline][cs_text]

The world’s tallest man in recorded history, Robert Wadlow. While he was not polyploid, gigantism in plants can occur from polyploidy.

Polyploidy in plants makes them bigger, hardier, and tougher. ⁽³⁾ Plants experience an effect called the Gigas effect. The greater the number of chromosomes, the stronger the effect. There is a diminishing return, however, as plants become genetically unstable the more times that polyploidy is induced. Additionally, results can vary, as noted in this scholarly article.

One other application of polyploidy in plants is useful — it can make sterile hybrids fertile again. Triticale (a hybrid of wheat and rye) is notable, because it can be made fertile through polyploidy. ⁽¹⁰⁾

To induce polyploidy in plants, we need to use a chemical named . Colchicine is normally used to treat gout in humans ⁽⁴⁾, and excess exposure to cochicine is considered toxic. In plants, however, it causes polyploidy.

[/cs_text][x_accordion][x_accordion_item title=”How to use Colchicine” open=”false”]First, you need some colchicine to work with. In medication form, it is purchasable online. The medication form is generally sold in 0.5 or 0.6 mg tablets, which works for our purposes. If you take ten of these tablets and mix it in a small glass of water ⁽⁵⁾, you have a solution that can work with plants. Be careful to wear gloves when working with this solution, as it is toxic to animals and humans.

On the plant you want to induce polyploidy with, brush the growing tips of the stem or meristems with some of this solution. After a couple days, examine the place where you applied the colchicine. If the plant looks different at the spot you put the colchicine and onward, then congratulations! You have successfully created a polyploid. You can take cuttings from this new growth to propagate more polyploids. If nothing seems to change, you can apply some more colchicine as needed until you notice a change.

If so desired, you can crossbreed back to an original, diploid strain to make a triploid plant. Triploid plants are infertile (do not produce seeds), and have a slightly diminished Gigas effect.

You can wash the colchicine off the plant later with water, so contamination should not be a problem.[/x_accordion_item][x_accordion_item title=”How Colchicine Works (In-Depth)” open=”false”]Colchicine works by preventing the formation of microtubules during mitosis. The centrioles, with no microtubules, cannot separate the chromosomes. The result is that you end up with some new cells that have double the number of chromosomes, and some new cells that have no chromosomes whatsoever. The ones without chromosomes are no longer capable of any function, and die out, leaving only the cells with double the previous chromosomal number.