Cannabis Breeding Methods: Selfing

Selfing is a very popular method among cannabis breeders as it can help them stabilize their strains much faster. However is it also a highly controversial breeding technique. Some view it as cutting corners and others even deem selfing to be unnatural. Let’s learn more about this trendy breeding method and see how you could use it to create your own cannabis strain.

What Is Selfing

Selfing or Self-pollination is a process where a plant can produce seeds without being pollinated by another plant. It happens when there is a transfer of pollen from an anther (male part) to a stigma (female part). When a plant pollinates itself, all the genes passed down to the offspring come from that same plant. The result of self-pollinating is a population derived from the same parent, known as S1. Then, every generation after that is S2, S3 and so on. The main way breeders do it is by reversing a female plant and using that feminized pollen to pollinate that same plant or its clone.

A Useful Breeding Tool

Unlike pollen Chucking, proper cannabis breeding consists of stabilizing strains so that they can breed true for a certain number of chosen traits. Usually this process starts after finding an outlier when doing a pheno hunt. In other words, after finding a plant displaying exceptional characteristics, breeders will then try to fix these traits so their new strain can become genetically stable. There are different breeding methods breeders can resort to in order to stabilize their lines. However, selfing is the fastest way to achieve stability (Homozygosity). Every time you self a plant, its offspring becomes 50% more genetically stable. Each gene only has 2 different alleles (2 different versions). Therefore, when self-pollinating a plant, there aren’t many possible combinations thus making genetic stability increase quickly. Even if selfing can allow breeders to create an IBL (In-bred Line) quickly, there can also be some serious drawbacks to using that method.

Selfing Pros VS Cons

Pros:

The fastest way to stabilize a strain:
As we previously discussed, selfing leads to a rapid loss of genetic diversity causing genetic stability to increase quickly. It is a great tool to fix certain desirable traits.
Need fewer plants to work with:
When using that method, breeders only start off with one plant. Because of that, it will be easier to find plants expressing the same interesting characteristics among the offspring. Consequently, breeders can create an IBL working with fewer plants than when resorting to Line Breeding.
Reveals the genetic mapping:
Provided you grow out enough seeds, selfing helps reveal which alleles are dominants and which ones are recessive. For instance, if about 75% of your S1s end up with green buds and only about 25% with black buds, then you can infer that the green bud trait is dominant and the other is recessive.
Shows how stable a strain already is:
If a plant is already a true IBL (Homozygous), then the S1s you make with it will display a high level of uniformity. If however after selfing a plant, you notice a lot of diversity among the offspring, then, you can conclude that the strain isn’t stable.

Cons:

Loss of vigor:
By quickly reducing the genetic diversity, selfing can lead to an inbreeding depression. This depression is characterized by a decline in vigor and overall fitness among the offspring. With this breeding technique, loss of vigor is almost inevitable. However, skilled cannabis breeders can minimize that decline by selecting the most vigorous plants generation after generation.
Infertility:
With each new selfed generation, there is a ever greater risk of loosing fertility. Either the offspring’ reversed pollen can become less viable or their female flowers may not be able to produce seeds after being pollinated. This is a relatively common problem so it is important to reverse several plants and/or pollinate several plants at the same time. That way even if some of them are sterile, you will still be able to make seeds.
Undesirable Traits:
When stabilizing a line, breeders can inadvertently fix undesirable traits. At some point, their strain may starts breeding true for some negative attributes. For instance, all of the offspring may produce brittle stems, mutated leaves or become hermaphroditic. This is even more likely to happen with selfing. That is why breeders should always keep seeds or clones from the previous generations. When they realize that they have fixed some undesirable traits, they’ll have something to fall back on.

Selfing Myths

All feminized seeds are S1s

Some growers call feminized seeds S1’s, S2’s…
While it is true that breeders can resort to selfing to make feminized seeds, it is not the only way.
One can also resort to line breeding, cross 2 different stable lines (true F1) or pollen chuck (F1 polyhybrid) in order to produce fem seeds.

S1s are stable

While it is true that selfing quickly increases stability, selfing a unstable polyhybrid just once will not make it stable. Its offspring will instead be quite diverse. In order to achieve stability, you would then have to repeat the process several times or do some line breeding. Therefore S1’s aren’t stable (Homozygous) unless the parent they come from was already relatively stable.

Reversed female cannabis plant.

Selfing isn't natural

Tomatoes, eggplants and chilli pepper for instance naturally self-pollinate. Even cannabis plants can sometimes self-pollinate as many weed plants have hermaphroditic tendencies. When female cannabis plants near the end of their life cycle, they sometimes produce a few male flowers as a last ditch attempt to reproduce. Although us humans cannot naturally have babies by ourselves, selfing is perfectly natural among plants.

Bonus Questions

Can You Self A Male Plant?

Just as you can reverse a female, you can also reverse a male by using an ethephon spray. Therefore you can also self male plants. However, the S1s made that way would give both female and male plants. Unlike female plants, males have both an X and a Y chromosome.

Can You Self several Times?

You can absolutely repeat the process several times. To do so, self-pollinate a plant you have selected among the offspring of the previous plant you selfed. However, each time you repeat the process, the risks of loss of vigor, infertility or bad mutations increases.

Although it takes knowledge and practice, self-pollination can be an incredibly useful tool to breeders and even home breeders.