How to select and prepare stock plants?

How to select and  prepare stock plants in plant tissue culture

If you are reading this article then congratulations! You are on the first step of doing plant tissue culture.

As we are delving deeper into different aspects of plant tissue culture, it is important to know more about the key points to prepare and select stock plants.

The process of tissue culture starts from the step of selecting stock plants. Stock plants are the plants that will act as mother plants with the desirable characteristics for micropropagation. An explant is a part of this stock/mother plant from which tissue culture will initiate.

Interestingly, an explant could be any part like meristems, shoot tips, stem pieces, nodes, buds, flowers, flower stalk pieces, anthers, petals, seeds, embryos, rhizome tips, root tips and so on. When we provide the right mix of nutrients to these explants, they develop into complete plants.

Another fact for us to know is that for most plants any type of explant you choose would work in tissue culture. However, there are certain plants which require specific explant for a tissue culture success. Here, we can consider the example of banana, which normally requires meristem tissues of plant (shoot tips) in order to produce disease free plants.

So this entire process to select and prepare stock plants comes under stage 0 of plant tissue culture. Hence, any micropropagation project starts with this stage for accomplishing further successful stages.

If you need to refresh your knowledge about plant tissue culture? Or want to know what are the different stages of tissue culture? Then have a look at our overview post on “Plant tissue culture: a short overview”.

For now, let us dive into different aspects of stage 0:

What is the number of stock plants selected?

Plants show a fascinating ability called ‘totipotency’ that enables any plant cell to develop into any desirable organ. As a result, we can use a single explant (plant part) to theoretically develop thousands of plants and this is one astonishing fact about plant tissue culture. Hence, even for a large-scale production, we need only a certain number of explants and mostly one stock plant would be enough to provide in the beginning of the culture process.

What is the optimum timing for collecting explants?

These explants could differ in size from as low as a microscopic 10th of a millimeter to as long as several centimeters of stem pieces. However, the timing to obtain an explant is crucial for the successful development of your desirable plantlets under sterile conditions. Hence, the most suitable time for you to obtain an explant is when the type of explant you are considering is in an active growth phase.

The younger the explant material is, the greater is the likelihood of its success!

It is also interesting for you to consider the time of the year when you cut an explant from the stock plant. Differences in temperature, day length, light intensity and water availability can affect the performance of your plants from year to year. These parameters can also influence whether the plant will be in the vegetative or the flowering phase as you might want to obtain explants in a specific phase of plant growth.

DID YOU KNOW?

For potatoes, the explant is actually the sprouts we see on them when kept for a couple of days in the kitchen.

What is the importance of stage 0 - select and prepare stock plants?

The stage of stock plant management is important as in this stage the standards of hygiene will undergo optimization. Also this process will determine for you, the quality and quantity of explants that will be set for the next stage. The stock plants which will be clean, insect-free, and diseases-free provide the best explants. These explants will have a higher chance of growing well for your in vitro setting.

There will be better results when your stock plants undergo fertilization and grow well in the greenhouses. This would (also) make it easier for you to identify the plant with the most desirable characteristics. This step is very important as it ensures that the large number of healthy plantlets ('clones') would be produced which are a replica of your chosen stock plant.

What are the measures to keep stock plants pathogen free?

There are a few steps that you can follow in order to keep your plant material free of disease-causing organisms.

  1. As a rule of thumb, the stock plants should stay in clean greenhouses or screenhouses. They should stay away from dust and diseases before obtaining explants. In this way, we can keep the plants as healthy as possible without any stress.
  2. In certain cases, special care can be given for short duration (2 weeks to 6 months). This could be done by washing the plants with clean water, fertilize and water the plants only at the base and by making sure that foliage dries properly.
  3. Depending on the plant species under consideration, you can test the plants for the known pathogens; specifically for viruses. You can do this with the help of agencies or by using a commercially available pathogen detection kit.
  4. One more method is to graft shoots on indicator plants that are sensitive to specific diseases. This process will show visually the symptoms in some hours or days.
  5. If the stock plants show symptoms of viral infection, it is also possible to treat them with heat (thermotherapy) and then meristem culture . It is noteworthy, that each plant species has a different threshold or limit to tolerate high temperatures for thermotherapy.

By keeping these steps in mind, we can ensure a good start for the entire tissue culture process, be it for small or large scale production.

We hope this article is helpful to all plant tissue culture enthusiasts. There will be more information on remaining stages as well. Stay tuned to this space!

By Nancy Bhatia | 13-April-2021

References

  1. Kyte, Kleyn, et al (2013) Plants from test tubes: An introduction to micropropagation. Timber press, Inc. 
  2. Bhojwani, S.S., & Dantu, P.K. (2013). Plant Tissue Culture: An Introductory Text. Springer India 
  3. Activity 5 - Plant Tissue Culture: Classroom Activities in Plant Biotechnology.Retrieved April 12, 2021, from https://www.apsnet.org/edcenter/disimpactmngmnt/labexercises/PlantBiotechnology/Pages/Activity5.aspx 
  4. Plant Tissue Culture. Retrieved April 12, 2021, from http://www.jiwaji.edu/pdf/ecourse/pharmaceutical/Plant%20tissue%20culture-converted.pdf