Creating a New Strain
Creating a new strain of weed requires passion and also patience. The process utilizes an understanding of genetics in the way of dominant and recessive traits to create a plant that can ultimately self-pollinate while consistently producing the new traits you would like to have expressed. This process can take multiple generations of cross-pollination, backcrossing, and self-pollination to create a suitable plant for making a new strain.
As a breeder gets started in creating their very own strain, it’s important to first identify the traits that they would like to have expressed. The aroma, coloration, taste, THC vs CBD ratios, and countless other subtleties are all determined by the genetic makeup of the plants involved. The first step in any breeding process is to identify these end goals.
Second, a breeder will identify the two parent strains that already contain all of the traits that they want in the new strain. These parent strains will pass down their traits to the next generation allowing us to selectively breed to isolate a new combination of the desired features.
Male and Female Plants
With an end goal established and parent strains picked out, it’s time to pick which parent will be the female and which will be the male. Female traits tend to be expressed more frequently in their children, so using female plants that are more closely aligned to the goal will create the best possible first generation to work with.
One male plant can produce enough pollen to pollinate roughly 20 female plants in a confined environment. Oftentimes as the plants mature, a plastic sheet will be placed over them or they will be separated from any other plants to ensure that no contamination occurs during the pollination process. The goal is to be sure that all female plants have been pollinated from our male source.
On the cannabis plant, female plants produce buds while male plants produce small pollen sacks. Each parent strain should be considered ‘pure’ in that they are consistently homozygous. This means that their children will consistently be the same due to the low variation in genetic outcomes possible from the combination of the parents.
As the pollen from our male plant interacts with the ovum of the female plant, the new genetic combinations will produce pairings to determine how the new genes will be expressed.
Understanding the Punnett Square and Genetic Terminology
Now, before we celebrate our first generation – we need to understand some middle-school genetics. The Punnett Square explains how different genetic combinations can occur and how they influence the plant.
An example Punnett Square could be:
| A | a | |
| A | AA | Aa |
| a | aA | aa |
Where ‘A’ represents the dominant trait and ‘a’ represents the recessive trait. In cannabis plants an example of this expression can be seen with green versus purple plant coloration. Where green is the dominant trait and will express itself as long as it has one ‘A’ and purple is the recessive trait and requires an ‘aa’ match to be expressed. The expression of a genetic trait in this way is referred to as a phenotype.
If you look in a mirror, you can quickly identify a number of phenotypes. Eye color, freckles, hair color, etc… all refer to the expression of genes and can be called phenotypes! Keep in mind, phenotypes can be made up of more than one genetic pairing as genes can influence or even mask one another.
We also need to understand heterozygous versus homozygous. Whenever we have a mismatch of dominant and recessive (‘Aa’ and ‘aA’) it creates a variable in the breeding and genetic processes. A cannabis plant that has a large number of these mismatched traits is considered heterozygous. However, if a plant has been bred to reduce the number of these mismatched pairings (now having mostly ‘AA’ and ‘aa’) then this plant is considered homozygous.
A pure strain is always homozygous, which means that when it produces pollen or ovum, we can accurately predict which genetic trait it will contain!
Heterozygous: A Closer Look
When creating a new strain, we need to understand exactly how a heterozygous pairing will impact our breeding process. Let’s go back to our green versus purple coloration and assume that we have a first-generation of plants with the ‘Aa’ pairing.
This is the case because our female parent was pure with an ‘AA’ genetic structure so it always passed down the ‘A’ dominant gene and our male parent was pure with the ‘aa’ genetic trait and passed down the ‘a’ recessive gene.
When growing our new strain’s first generation, every plant will display green coloration, which if we didn’t understand the genetics at play may lead us to believe that this is a pure trait. However, as these plants mature and if they self-pollinate, this mismatched pairing creates the Punnett Square situation. Each plant could release pollen or create ovum with either the ‘A’ or ‘a’ trait at a 50% chance for either. During this self-pollination process, we end up with a second generation of seed that will have 25% ‘AA’, 25% ‘Aa’, 25% ‘aA’, and ‘25% aa’.
First-generation children in the hybrid process are stable and a unique plant since we can predict the outcome through their parents, but they are not considered a new strain because they cannot be self-pollinated to produce a consistent outcome.
Second Generation and Backcrossing
Once a breeder has a hybrid or cross-strain that they are happy with, it needs to be refined from being heterozygous to homozygous. In other words, we need to start to identify the traits that can vary from generation to generation to convert them from a mismatched ‘Aa’ or ‘aA’ pairing to the homozygous ‘AA’ or ‘aa’. This process can take countless iterations, so we have to be patient!
This may mean that some desired traits are lost since it is possible for mismatched traits to produce a unique outcome. An example of this is often seen in flowers where mismatched pairing can produce unique coloration. A red and white flower bred together may produce a pink phenotype using this ‘Aa’ genetic pairing.
However, to truly be a new strain, mismatches must be resolved.
A common way to do this is by utilizing the parent strains in a process known as backcrossing. In our new strain, we may have a number of mismatched ‘Aa’ characteristics. To resolve this, we first need to identify if this is a dominant, recessive or hybrid feature. We can do this by examining a second generation.
In the second generation, a dominant feature would be expressed 75% of the time and recessive the remaining 25%.
If this feature is instead hybrid, we would find that 50% of second generation plants exhibit the trait (‘Aa’ and ‘aA’ pairings) but 25% of the time we would get the result of the ‘AA’ pairing and 25% the ‘aa’ pairing. In this case, we would need to identify which trait (‘AA’ or ‘aa’) our pure strain would end with.
Creating a Pure Line – The New Strain
Once we know our end goal (‘AA’ or ‘aa’) for our phenotypes we can backcross with the parent that already has this established genetic trait to improve our odds for creating a next-generation that is consistent. A first-generation with an ‘Aa’ trait when combined with a parent whose genetics are ‘AA’ would produce 50% of the children with ‘AA’ and 50% with ‘Aa’. Controlled breeding in this way significantly improves the chances of creating a plant in a generation with the desired outcome.
Through iterations of self-pollination and backcrossing, we can identify mismatched traits in our heterozygous plants and eliminate the mismatches, eventually creating plants with homozygous traits instead.
The ultimate end goal is that when we allow our new strain to self-pollinate, there is no variation from generation to generation. When this has been achieved, then we have officially created a new strain!
A Practical Example
To fully understand this process, let’s create a slightly more complex example.
New Strain Genetic Goal:
‘AA’, ‘BB’, ‘cc’, ‘dd’
Parent (Female):
‘AA’, ‘BB’, ‘cc’, ‘DD’
Parent (Male):
‘AA’, ‘BB’, ‘CC’, ‘dd’
First Generation:
‘AA’, ‘BB’, ‘Cc’, ‘dD’
With our first generation genetics existing as a ‘known’ due to homozygous parents, we can now begin making some decisions to manipulate the genes to our final goal.
We can begin by taking our first-generation females and backcrossing them with the male parent strain. Thanks to the Punnett Square we can see that 25% of the resulting offspring will have our desired result of:
Backcrossed Second Generation:
‘AA’, ‘BB’, ‘Cc’, ‘dd’
First, as these plants mature we will separate all that have the ‘dd’ recessive phenotype showing. We’ll self-pollinate with these plants in multiple groups of 20 females and 1 male.
Since we cannot be sure if these plants have the ‘CC’ or ‘Cc’ genetic combination, we want to create multiple batches while controlling the male plants. With multiple male plants and even more female plants being used, we will be able to ensure that some plants within the resulting generation have our final desired traits:
Third Generation (Some):
‘AA’, ‘BB’, ‘cc’, ‘dd’
While the 3rd generation is maturing we will separate out all plants that display both the ‘cc’ and ‘dd’ phenotypes and allow these to self-pollinate again in multiple groups of male/female pairings.
If we have successfully created our new strain, then every resulting plant from this separated third generation will mature with the same genetic pattern as their parent!
And with that, a new strain has been cultivated!
In Summary
Creating a new strain requires a significant amount of patience, understanding of the genetic processes involved, and manipulation of dominant and recessive traits through the use of backcrossing and self-pollination.
Here at Kind Care, our team is constantly working to develop new strains to improve qualities, traits, and ultimately create new experiences for our customers. If you would like to learn more, our staff would love the opportunity to talk more at our store in Longmont and to maybe brag a little ourselves as we show you some of our latest creations!
