Making hybrid cannabis crosses

By Tony, Dutch Passion

Selective breeding, or artificial selection

Sometimes a breeder has a specific goal in mind when breeding cannabis. The search for a particular trait may follow a process often collectively known as selective breeding, occasionally it is called artificial selection. That’s where parent plants are selected for a particular quality, such as a fruity aroma, or an appealing taste, or big buds. By crossing parent varieties with the genetics for a similar trait you are increasing the chances that the offspring will also share those characteristics. With selective breeding there are further tips and tricks which breeders can use to further increase the consistency and genetic similarity of the seeds. For example, a plant can be back crossed with a parent or grandparent to further increase the chances of a particular characteristic being expressed in the offspring. Back crossing is a powerful tool, but it has to be used correctly. If back crossing is done in the wrong way (‘heavily inbred’) it can stabilise the wrong kinds of properties.

Hybrid F1 crossing

On other occasions a breeder may try something altogether different, and cross two quite different and genetically diverse varieties. This is quite a different breeding philosophy to selective breeding. With a hybrid cross you are taking two separate gene pools and mixing them together hoping to produce something that is better than either parent. The results can both surprise and disappoint, like many things in life perseverance and effort can often be rewarded, but there is no guarantee. When two different cannabis cultivars are crossed you don’t necessarily get an immediate 50/50 blend of the genetics, that can take lots of hard work to fine-tune. But one of the real benefits of creating a hybrid is that the growth may show significantly improved form and speed, better than either parent. This is a process known as Heterosis, it has been manipulated many times by breeders of traditional farm crops such as Maize. This phenomena is also known as ‘outbreeding enhancement’ and cannabis growers may be more familiar with the other terminology for heterosis which is ‘hybrid vigor’. If the cannabis hybrid has its traits enhanced as a result of combining the different genetic contributions from the parent cannabis varieties it is described as showing hybrid vigor. Cannabis breeders will be aware that hybrid vigor (heterosis) can come from a complicated genetic inheritance known as Mendelian or non-Mendelian inheritance.

Heterosis, or hybrid vigor.

Hybrid vigor is one of the real benefits of a hybrid cannabis variety for the home grower. Seeds produced from crossing two distinct cannabis varieties can grow with more speed and strength than either parent. That can mean larger harvests, faster bud development and ultimately more THC and cannabinoid production. Seeds produced by hybridising two different cannabis varieties are often called F1 seeds, or ‘first generation’ crosses. F1 cannabis seeds can only be produced by crossing two specific parent plants, and usually the cannabis breeder will have looked at numerous parent plants before deciding on the final two plants. A good quality cannabis hybrid is often the result of months or years of work and the parents are highly prized and well cared for. Once one of the parent varieties disappears/dies so does the F1 hybrid. If you cross F1 seeds together you will get an ‘F2’ or second generation cross which may not be quite the same as the original F1 cross.

F1 cannabis genetics.

The extra grow vigor from an F1 hybrid is evident both during growth and harvest. During growth the F1 hybrid will grow with unusual speed and force, the plants may grow taller and wider with more side branching than you would expect. During bloom the buds grow faster and larger, you may see heavier harvests from an F1 hybrid than you would from either parent variety. But the improved growth and yield that comes from F1 hybrid heterosis is not as pronounced from F2 (second generation) seeds. As long as you continue to cross genetically different varieties you will see the F1 vigor in the offspring.

Limitations of hybrid vigor and heterosis.

Breeders often talk about the benefits that can be offered by a good cannabis hybrid showing F1 vigor. But its not so common to hear of the issues and challenges faced when trying to create a good hybrid. F1 hybrids are often homogenous and grow with vigor, but they can show instabilities as well. One result of the uncertainty regarding stability is that breeders have to perform extensive testing on the F1 seeds before release to ensure consistent growth characteristics. And when its all done correctly, a good cannabis hybrid can deliver exceptional results. Usually parents are selected to be rich in THC, genetically different, stable and with good yields. Its no guarantee that the F1 hybrid will be perfect, but its the best way to start.

Parent selection for hybridisation

Usually the best cannabis breeders will make several hybrid attempts and grow seeds from them all, looking for the best expression of hybrid vigor and of course the highest THC/cannabinoid analysis results. These days laboratory cannabinoid analysis is an important aspect of breeding, it allows the professional breeder a comprehensive understanding of the quality of the parent plants and the offspring. With professional lab analysis the job of hybridising cannabis varieties is made significantly easier and allows the breeder a transparent comparison of the results and progress. It also allows the breeder to quickly discard ineffective breeding lines and focus on the best approach. Often there will be several specially selected parent plants from each of the two varieties being hybridised. The best breeders will know the cannabinoid profile of all the parents, and usually these are all selected for e.g. high THC levels and heavy yields. But the important part of the hybridisation is seen when the first batch of seeds is produced from the two different parents, a successful hybrid is one which outperforms either parent in growth and retains excellent THC levels and heavy yields. Often the breeder will prefer the fastest blooming result, or perhaps the easiest growing F1 seeds. These days most cannabis growers leave the job of cannabis breeding to the specialist seed companies. And the advice to home growers remains the same, you don’t use that many cannabis seeds each year so get the best genetics you can from a seed bank that you can trust. And enjoy your home grown cannabis!