The Benefits of Tissue Culture Techniques in Cannabis Cultivation
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With the growth and expansion of the cannabis industry in recent years, cultivators have come under pressure. The significant amount of space, time, and manpower needed to run traditional grow operations threatened to limit an industry looking to maximize its yield per square foot while still maintaining the high-quality standards that cannabis connoisseurs expect from today’s established operators.
Plant tissue culture propagation has been widely used in other areas of commercial agriculture for decades, but it has only recently been taken up by the cannabis industry as the sector gained more legal recognition. Such in vitro plant propagation techniques offer an improvement over the traditional propagation of plant cuttings or cultivation of seeds, Dr Veronica Codesido, co-founder and manager of breeding and cultivation at MIFCO Biosciences, told audiences at the Analytical Cannabis Expo Europe Online 2021.
“You are going to obtain higher cannabinoid yields with a lower production cost, virus-free plants, plants that are independent of environment, and that can be harvested in short duration,” Cosesido said. “And importantly, it is the best method to maintain and safeguard plant stock.”
Optimizing the cannabis grow operation
Most traditional cannabis operations cultivate plants with cuttings taken from a mother plant. These cuttings can be re-planted in soil and grown into new plants that are effectively clones of the mother plant, retaining its favorable characteristics and genetics. Keeping these mother plants healthy and free of disease can be a challenging task for cultivators, and bringing the clones to maturity requires significant amounts of time and space if the plants are to grow with enough vigor.
Conversely, tissue culture cultivation techniques start with tiny samples of viable plant tissue – sometimes just a part of a cell – which can be used to produce hundreds of genetically identical clones of the mother plant. The next steps will depend on the exact tissue culture technique being used, but, generally, the small tissue samples are established in tubes containing a specialized culturing medium. After a few weeks, shoots will begin to develop and grow into new young plants, which can be transferred out into larger pots.
“If we compare classical breeding with tissue culture breeding, the first step is the same: choose the best plant, normally based on the phenotype,” Cosesido explained. “But then you need to make clones. And what happens when you need to make clones [traditionally] is that you need a very enormous surface to maintain those clones. Compared with in vitro culture, you only need small tubes.”
Using such an in vitro cultivation technique, cultivators can easily experiment to find the ideal growth conditions for the cannabis strain being cultivated. The growth media contained in the tubes can be altered to contain the most optimal nutritional content for healthy growth, and the addition of plant growth regulators and hormones can be carefully monitored to ensure the correct balance is reached. With these tissue samples needing less space to propagate than large cuttings, it may also be easier for cultivators to adjust different environmental factors to ensure healthy growth.
“You can control everything using in vitro culture [methods] and understand how your plants are going to perform in different environments,” said Cosesido. “You can control all of the things necessary for your crop, such as the humidity, the temperature, the light. And understanding the light spectrum, photoperiod, and intensity of the light also.”
Tissue culture techniques can transform the way cannabis is grown
There are a variety of different tissue culture techniques that can be used to great effect for cannabis cultivation.
For example, the meristem culture technique is a particularly strong tool for cannabis cultivation as it allows cultivators to produce virus-free clones of a mother plant using a sample of the apical meristem. These clones can also be multiplied at the commercial scale to produce even more virus-free plants.
“These meristems have no vascular connection to the developing procambium, leaf primordium, or axillary buds,” Cosesido explained. “So, if you have any pest, any disease, any virus on your plant, this disease still won’t arrive at this meristem.”
Protoplast culture methods rely on the protoplast, which is the term given to the internal workings of a plant cell. The method starts with a naked cell that has been mechanically or chemically stripped of its cell wall, which is then cultured in a favorable medium and allowed to regrow a new wall, divide to form cell colonies, and ultimately develop into a young plant. This method presents an interesting opportunity for the use of gene editing technology, such as CRISPR cas9 gene editing, and other similar experiments with genetically transformed plants.
MIFCO Biosciences is already using cutting-edge micropropagation tissue culture technology in its growth operation, Cosesido says, with noticeable savings in plant health and production efficiency.
“The space to produce 1000 cuttings in square meters is around 3-5 for traditional manual cloning, compared to only 0.36 square meters if you use tissue culture cloning. More importantly, the [number of] clones processed per person per day – in traditional cloning, a person could achieve 200 to 250 clones per day, however, using tissue culture, the same person could achieve 1500 to 2000 clones,” Cosesido said.
“There are some other considerations that are very important, like cleanliness. In traditional manual cloning, you have a chance of contamination where in vitro culture you can have disease-free and virus-free certified plants. If we talk about vigor, in traditional manual cloning there is a chance of reduced vigor from stressed or infected month plants, but [with tissue culture cloning] you have improved vigor from meristematic reviving.”
With better plant health and improved vigor, the final cannabinoid yield from the plants can also be enhanced by around 10-20 percent. Taking all of the production costs, processing times, and other operating factors together, MIFCO Biosciences estimates that tissue culture cloning can potentially result in estimated revenues that are ten times greater than a similar operation using traditional manual cloning.
The future outlook for tissue culture techniques
While tissue culture cultivation has been used in other areas of agriculture for decades, that does not mean these techniques are already perfect. Cannabis-focused biotechnology companies are now investigating how these methods can be further optimized to suit commercial cannabis grow operations.
Combining tissue culture micropropagation technology with bioreactors is one of these new fields of advancement. In essence, these bioreactors would provide a small, fully controllable ecosystem for the cannabis plants to develop and grow properly, while eliminating the need for support substances, such as agar. The inside of a bioreactor can also be kept complete aseptic by connecting it to a sterile air delivery system, thereby eliminating the chance of infection and improving plant quality. Designing bioreactors that are appropriate for cannabis strains – ones that can accommodate the size of the plants, tolerate the grow light intensity, and otherwise provide ideal aeration and ventilation – could represent an important step forward for cannabis cultivation.
Similarly, some biotechnology firms are experimenting with automation and robotic subculturing technologies in order to reduce largescale operation costs. While these systems may be prohibitively expensive for smaller operations at this time, in the future, these automated systems could greatly improve the throughput of cannabis cultivation operations.
This article originally appeared in Analytical Cannabis' Advances in Cannabis Cultivation eBook in December 2021.