Plant Tissue Culture: The Future of Cloning is Here
Plant tissue culture is gaining traction as a method to capture outstanding genetics. Previously employed only by large corporations, with the right equipment home growers can also benefit.
Many states are still riding the wave of cannabis legalization and while it has slowed down somewhat from the initial push, acceleration in marijuana research area has expanded. Legalization has burst open the doors for research, giving everyone better access to knowledge and types of cannabis. Plant tissue culture has begun to gain a foothold in the cannabis industry and is the future of change within the industry.
Cloning with Plant Tissue Culture
Seeds and clones have been the only choices for many growers and breeders until recently. Growing from seeds helps reduce contamination of pest and fungi but gives a high variability from its mother plant. For those trying to get an exact copy, cloning is the next best option. However, clones can transfer pests into an environment and can require more care, but not everyone can access these genetics. Plant tissue culture may overcome many of these issues.
Plant tissue culture is also referred to as micro-propagation, and in-vitro propagation is considered another form of cloning. In simple terms, plant tissue culture is cloning plant tissue in a laboratory environment. In realistic terms, plant tissue culture is cloning plants in a controlled environment, with dedicated staff, and access to outstanding genetics.
Agricultural sectors such as orchids, strawberries, potatoes, roses, and many others all use plant tissue culture. They have proven that with a little bit of working material thousands of clones can be produced quickly. Where direct-stem cloning has its limitations in growth area, disease control, pest control, method, and cost, plant tissue culture can limit or remove these factors. If implemented properly plant tissue culture can preserve genetics, increase production volume, and quickly expand any grow operation. For breeders, plant tissue culture allows for reaching more people with their genetics. For growers, it means better access to genetics and decreases in the price of clones.
Before we dive into more details of plant tissue culture, I should make it clear that it has nothing to do with genetically modified organisms. Although it is used in genetically modified organisms work-flow, nothing is changed in the plant when using only plant tissue culture. Plant tissue culture is often employed by large companies, but with access to equipment, anyone can do it at home.
The Plant Tissue Culture Process
It all started in the mid-1800s, when it was shown that cells from plants and animals could be grown outside of the original organism. For almost 50 years nothing of note happened for this method until the early 1900s when it was proven that medically significant cells could be grown in culture in a nutrient solution. Plant tissue culture was then accelerated as agricultural significance was proven. Fast forward to the present day and many significant agricultural industries use plant tissue culture.
Plant tissue culture can be done via two different processes. The first process is removing a cutting of about one-third to just over an inch (1 to 3 centimeters) long and growing it in media. The second process involves removing 1-5 millimeters of cells and growing them in media. Both processes produce an exact copy of the plant. Cuttings are taken from leaves, roots, apical meristems, or stems. Where the cells are cut from influences the success of growing a plant copy. The most desirable cells are obtained from the apical meristem. These are the cells at the tips of the roots and shoots of the plant. Apical meristems represent cells that grow quickly and are disease-free.
The plant material is placed onto agar gel with a selective solution of media and growth hormones. The plant material is shelved under low light. Growth hormones that promote shoot and leaf development are added to the media. After a healthy structure is developed secondary hormones to promote root development are added. This is usually the preferred method as true roots are developed from healthy stems.
After shoots and roots are developed, the plant then grows to a determined height. Then an acclimatization process is needed. This process will help to harden off the plant and allow it to experience its growing environment. During this process, many plants are often lost to fungi, low immunity, or environmental attack. Currently, research to reduce loss suggests adding beneficial fungi during the process preserves more plants.
After the acclimatization process, the plants are ready to be placed in starter soil and will grow normally after a couple of weeks. Since the plants are all copies of each other, genetic bottlenecking takes place. Genetic bottlenecking is when a group of plants all share the same genes. While this can decrease genetic variability and result in unforeseen population loss, different protocols can decrease these problems. I believe it is always important to share clones with your local community, have a breeding program in place, have different mother plants from the same species on hand, establish beneficial bacteria, and pest control in your plant tissue stock.
Is It Difficult?
Small scale or home-based tissue culture is not very difficult. With some general lab tools, sterile equipment, and a little bit of knowledge anyone can do it. However, it can be expensive, time-consuming, and labor-intensive. Small to commercial-scale labs can have a higher output and be cost-effective.
Large-scale production requires a dedicated lab, knowledgeable staff, and lab-grade equipment. While small scale has its benefits to keep costs down, the volume of plants determines their profitability. If volume is achieved, the cost of each plant can be $1 or less.
However, if climate conditions are not calibrated perfectly entire stocks can be lost within days. For a home grower, the most difficult part is setting up the lab. The larger the growing stock becomes the more difficulties can occur.
What is Needed?
To set up a house or small-scale plant tissue culture lab some investment in equipment is needed. Here is a list of equipment I use:
pH meter: used to test the pH of media and other liquids. Digital is best but some still use pH testing strips for liquids that doesn’t require much accuracy.
Scale: with two decimal places and measures in grams.
Glass containers: 250ml and 500ml, it is cheaper to buy them in boxes of 100.
Plastic containers: these are used for holding lab equipment and other cleaning chemicals. Can be used for growing containers but don’t last as long as glass.
Glassware: beakers, flask, volumetric flask, large glass bottles, graduated cylinders, and glass bottles for plants. Glass bottles can be in any size you want, though I prefer 250ml and 500ml versions.
Pipettes: Glass pipettes reduce plastic waste and are relatively cheap; there are more accurate semi-automatic pipettes. I don’t like them as they require consuming plastic tips and need calibration.
Autoclave: some people use a pressure cooker, but I use a small 24-liter electric one. A real autoclave goes through a series of heating, steaming, and pressurizing at specific intervals. Spending the extra money on a dedicated system will help in the long run.
Laminar flow hood: These can be made cheaply. A laminar hood is a box with an exhaust fan, UV light, and HEPA filter. This is the most expensive part of all the equipment but is not completely essential. However, you will need some sort of hood to reduce contamination and inhalation of chemicals. If you buy one, ensure it is very clean at all times. Most contamination will occur in this area, which can be reduced by cleaning it before and after every use.
Gelling agents: Agar gel is made from seaweed and used extensively in plant tissue culture. I prefer lab-grade because it is very pure, relatively cheap, and a consistent product.
Nutrient media: nutrient media provides all the macro- and micronutrients for your plants. The most common media used is Murashige & Skoog (MS) media. Others exist but MS is the most general one used for most plants.
Growth hormones: Used for shoot, leaf, and root development.
Washing area: this will be the area where all your glassware is cleaned and dried.
Culture Room: This is the room where all the plant cuttings are grown. This room should be temperature controlled, have multiple leveled shelves, and lighting for each shelf. T5-T12 lights are used, however, more people have switched to more cost-effective LED lights. Lights should be white as the plant needs the entire spectrum to survive.
Most plant tissue culture labs have separate rooms for each stage of the process. For example, a washing room, media preparation area, transfer room, and culture room. This is used more for commercial-scale operations as it helps to decrease contamination, increase work flow, and decrease time spent at each stage. For small or home-scale operations it is best to dedicate one room big enough to have all four areas.
Advantage for the Cannabis Community
This technology serves the purpose of developing plants that are disease-free and exact copies of their mother. Plants can also be grown quickly with consistent quality at industrial scales. Plant tissue culture provides the cannabis industry:
- Identical strain characteristics
- Genetic preservation
- Production speed
- Requires less starting material
- Healthy disease-free plants
With all these benefits, more companies and people should consider adopting plant tissue culture into their growing operations. As the industry grows, I expect the price of clones to be reduced and for seeds to become less available. One day, maybe, when you order your favorite strain you will be picking up a lab-grown plant from your mailbox.
Written by Luis Cordova | Plant Biotechnician, Pharmaceutical Scientist
Luis holds a M.S. in Plant biotechnology and Pharmaceutical Science. He is a long-time cannabis grower He has put his focus on breeding cannabis and development of organic soils for tropical regions. He loves how much the industry has grown and changed. He hopes to pass on new and old knowledge to all growers across the world.