Cannabis Breeding Basics: F1 Hybrids and Beyond

Breeding cannabis can be an extremely complicated and time consuming process. In order to identify and stabilize a sought after trait, it may take multiple generations and hundreds, if not thousands, of plants. This is why most breeding operations are left to the professionals who have sizable facilities dedicated to breeding. This is not to say that basic breeding cannot be done in a cannabis hobby garden. In fact, some of the most unique cannabis strains available were created by home growers; in some cases, by complete accident.

One aspect of cannabis breeding that is different than most vegetable breeding programs is that cannabis plants are dioecious, meaning they have separate female and male plants. Most vegetable plants are monoecious plants, meaning they have both male and female organs on a single plant. Dioecious plants are more complicated to breed because the breeder must pollinate a female plant with pollen from a male plant. Seeds generated from cross-pollination of two plants will produce more genetic variation than seeds created through a self-pollination (monoecious plants) technique and, therefore, requires more time and effort to find and stabilize a sought after trait. Basically, don’t expect to be providing the next great hybrid on your first attempt at cross-pollination. Before purchasing seeds or beginning a home breeding program, it is a good idea to have a basic understanding of cannabis breeding techniques and terminology.

Landrace Varieties

Chances are good, if you’ve researched cannabis breeding, you have come across the term “landrace”. A landrace variety is a type of cannabis that has established itself in a particular region and has grown there wild for a very long time. Essentially, landrace cannabis strains are strains that are native to a particular area, where they developed naturally and have grown wild for millennia. Because of their natural stabilization through natural selection, landrace strains are stable, robust genetics that produce homogeneous offspring. In other words, landrace strains from a particular area will display very similar growth patterns, appearance, and cannabinoid/terpene profiles.

There are many landrace strains from around the planet. Landrace varieties are the foundation for most cannabis breeding programs, as breeders can expect little variation between landrace species of the same variety. Because landrace strains (of the same variety) exhibit similar growth patterns, appearance, and cannabinoid/terpene profiles, they make a solid starting point or building block for breeders.

In-bred Line (IBL)

In-bred line, or IBL, refers to cannabis strains made from crossing two almost identical genotypes. Breeders use this technique to acquire desirable traits and stabilize the genetic line. There is usually a lot of work behind each IBL strain as a large population of pure specimens has to be used to select the correct parents for breeding. Breeders who make IBLs also must face the issue of inbreeding depression, a result of crossing plants with very similar genetics. In many cases, inbreeding produces less than desirable traits and breeders must sort through hundreds, if not thousands, of offspring to find the particular stabilized traits they desire. The end goal of IBL is usually to create a highly stable variety for seed production.

F1 Hybrids

An F1 hybrid is created when a breeder crosses two unique genotypes (from either two landrace strains or two IBLs) and creates a first generation hybrid; for example, crossing two completely different landrace strains from different geographical locations. This might be done to create a hybrid that exhibits a sought after trait from each of the different parent plants. If both parent plants are very stable, the result is generally a very uniform offspring. One of the main reasons F1 hybrids are sought after is that they will show the so-called “hybrid vigor”. Hybrid vigor refers to how F1 hybrids will often have special attributes, such as enhanced yields, a shorter time to harvest, and/or a heightened resistance to drought or diseases.

Poly-Hybrids

Many of the seeds sold in cannabis shops or the seeds created by hobby growers are considered poly-hybrids. Poly-hybrids are crosses between two different hybrid strains. In most cases, the offspring of poly-hybrids are quite unstable. In other words, the offspring of a poly-hybrid will not necessarily produce the specific traits of either parent, but, instead, may exhibit a wide variety of traits derived from its entire lineage. This is why a home grower should not expect his or her poly-hybrid to be as homogeneous as a true F1 hybrid. However, sometimes a grower gets lucky and produces a poly-hybrid that is stable and exhibits unique attributes.

F2, F3, F4, F5…

When a horticulturist crosses two F1 individuals (landrace, hybrids, or poly-hybrids) a second generation, or F2, is created. As more generations are bred, they are referred to as F3, F4, F5, and so on. An F2 generation often produces a more diverse offspring, where more varying traits of the parent plants are exhibited, than an F1. With an F2, growers should expect 25% of the offspring to resemble parent A, 25% to resemble parent B, and 50% to be a mixture of traits from both parents. Breeders looking to stabilize a particular trait will continue to create subsequent generations (F3, F4, F5, etc.) until a generation is developed that produces uniform offspring with the desired traits. Again, this is why some aspects of breeding are best left to professional growers with facilities large enough to house all the plants necessary to stabilize the sought after traits.

Backcrosses or BX

Backcrossing, or BX, is a breeding technique generally used to correct a particular trait. Backcrossing is done by crossing one of the offspring (F1, F2…) with one of the original parents (the parent with the desirable trait). Breeders will also cross the backcrossed offspring with the parent again to further stabilize that parent’s desired trait. Backcrossing is also used to replicate a clone in seed form. For example, let’s say a grower has a female clone and wants to create seeds that produce offspring similar to that clone. This can be done by choosing a male plant to cross with the clone and then backcross the offspring (with the original clone) as many times as needed until the offspring exhibit traits similar to the original clone.

Selfing (S1) Feminized Cannabis Seeds

Feminized seeds are popular among hobby cannabis cultivators. Feminized seeds will produce female plants instead of both female and male plants. In breeding, S1 refers to the first generation produced as a result of crossing a female plant with herself. This can be achieved by utilizing techniques that reverse the sex of the desired female plant to get it to produce male pollen. The male pollen produced by the female plant is then used to pollinate that female plant and the resulting offspring are S1 feminized seeds. Techniques used to get a female plant to produce male pollen include the use of particular chemicals (such as colloidal silver) or rodelization. Rodelization takes advantage of the fact that a female plant will, toward the end of her life, try to pollinate herself as a last ditch effort to produce offspring. By stressing a female plant during her flowering cycle, breeders can manipulate the female plant to create a few pollen sacs. The pollen produced by the female can then be used to self-pollinate that female and create S1 feminized seeds. When S1 plants are backcrossed with the original female plant, they can create S2, S3, S4 generations and so on. This is often done by breeders to preserve a particular strain’s genetic traits.

Although cannabis breeding can be extremely complicated and time consuming, hobbyists shouldn’t shy away from experimenting with breeding. The poly-hybrid strains a hobbyist is most likely already growing may not produce the most stable offspring, but it could still be bred to create something unique. In theory, if a home grower does get lucky and creates a strain with unique attributes, he or she could use a backcrossing technique to produce seeds that would make plants like his or her masterpiece.

When shopping for cannabis seeds, a basic understanding of cannabis breeding terminology will not only help a grower make sense of what they are purchasing, but also what to expect from that particular genetic. Professional breeders who have the area and time to produce truly stabilized offspring are the best bet for purchasing unique, but stable, strains. Professional breeders also continue to create and develop cannabis strains for very specific purposes (such as high CBD strains for particular medical ailments). There is no doubt, as cannabis laws continue to change in favor of legalization, that more reputable breeders will be established and even more new, unique cannabis strains will be developed. This is not only great news for cannabis enthusiasts, but also for the medical community where sophisticated cannabis breeding programs could be the key to unlocking new, powerful treatments and cures.

Eric Hopper resides in Michigan’s beautiful Upper Peninsula where he enjoys gardening and pursuing sustainability.