Tissue culture, also known as micropropagation, is a widely used technique for cloning plants that is pretty common practice in agriculture and horticulture yet has only recently been applied to cannabis. When done right, the use of cannabis tissue culture can produce huge numbers of disease-free plants, while the fact that cultures can be stored indefinitely and take up minimal space makes this an excellent method for banking genetics.
How Does Tissue Culture Differ From Cloning Cannabis Plants?
Traditional cloning involves repeatedly taking cuttings from a single mother plant and growing these in a potting mix that contains the right nutrients and hormones to allow for the development of roots. It’s a great way to generate new plants quickly, yet it comes with many drawbacks that can be eliminated by switching to cannabis tissue culture.
For one thing, cloned plants are highly susceptible to diseases and pests and will carry any illnesses that the mother plant may have been harbouring. For instance, hop latent viroid is a type of virus that is thought to regularly inhibit the development of clones, preventing them from reaching their potential.
With cannabis tissue culture, this problem is nullified. Tiny cuttings can be taken from any part of the plant. However, many micropropagators choose to take their samples from the meristem, as this tissue contains no vasculature through which pathogens may travel. Cuttings are then fully disinfected by dipping in an alcohol or bleach dip, which totally eliminates any disease-causing microbes.
Starting with completely clean tissue is a major benefit of micropropagation and gets around one of the biggest obstacles associated with traditional cloning.
The removed cuttings – now referred to as explant material – are then introduced into a growing medium such as agar, which contains the right blend of nutrients and hormones to stimulate growth. After about a month to six weeks, the cannabis tissue culture is transferred to another medium containing rooting hormones, thus encouraging them to grow roots.
All of this must be performed under sterile conditions, as contamination can destroy cannabis tissue culture and is the most common cause of failure. Therefore, a cleanroom must be set up, with all environmental aspects such as airflow and humidity being tightly controlled and all surfaces regularly disinfected. Performing all tasks inside a laminar airflow hood is one way to achieve the necessary level of cleanliness and is something that many serious micropropagators rely on.
When the plant is large enough, the grower can dice it up into hundreds of new plants, each of which must be disinfected and then cultured before finally being hardened off as it is introduced to its final growing environment.
By the end of the process, cultivators can end up with huge numbers of genetically identical, healthy plants.
The Benefits Of Cannabis Tissue Culture
The sterilisation of cuttings is seen as the most important step in the cannabis tissue culture process, as it ensures that the resultant plants are free of pests and disease. Yet while this may be the main advantage of micropropagation in many people’s eyes, it is far from the only one.
For one thing, tissue culture provides a method for creating huge numbers of cannabis plants without taking up much space. While each clone needs its own little pot, tissue culture cuttings are tiny and can be kept in small petri dishes or vials while they are developing. As a general rule, micropropagation is said to require about a tenth of the space needed to generate clones using conventional methods.
In addition, tissue culture eliminates the need to store, protect and maintain a mother plant, as each cutting can be multiplied indefinitely to create more copies of itself. Not only is this another space saver, but it also cuts out a lot of work while significantly increasing the number of plants that can be produced. Therefore, tissue culture may be of particular benefit to medical cannabis users, who often require large quantities of weed and depend on stable genetics.
Another benefit of not needing a mother plant is a reduced risk of “sporting”, which occurs when the mother accumulates mutations over time due to environmental stress and passes these on to any clones that use her genetics.
For many, however, the major advantage of tissue culture lies in the fact that it is an excellent way to bank cannabis genetics. This is because growers have the power to keep cuttings in a perpetual state of suspended animation by simply not adding the rooting hormones and can therefore store their tiny, pest-free cuttings for as long as they wish.
Of course, there’s always a flip-side, and it’s worth considering some of the disadvantages of cannabis tissue culture. For one thing, it takes a lot longer than traditional cloning, with the whole process requiring up to three months to generate a mature plant. That said, the technique does allow for the production of many more plants than cloning does, so the overall time to plant ratio may still be favourable.
The costs and effort associated with creating a cleanroom are another drawback, yet this can always be overcome with a little creativity. For instance, some growers choose to rig up a makeshift clean box using a fish tank and some piping.
While the technique is yet to become widespread among home growers and several gaps in our collective knowledge about cannabis tissue culture remain, the method is increasingly being touted as the future of the cannabis industry. After all, if it can be used to regenerate entire redwood forests, then it must be worth all the fuss.