OVERVIEW

What if the plant culture you are working with gets infected!

What are you going to do? How are you going to grow the plant in mass without any infection? How are you going to remove infections from plants?

There is only one optimal way to deal with this dilemma; tissue culture of plants.

Tissue culture is a wonderful and most popular technique in agriculturists or horticulturists because of its multiple advantages. It helps culturists to produce large numbers of plants and disease-free plants. The technique has recently gained popularity in Cannabis growing industries. Cannabis is cultured in several parts of the world for its medicinal properties. However, these plants are sensitive to bacterial, viral, fungal, or pest attacks. This makes the growing processes of Cannabis challenging and difficult. The tissue culture technique implements the best solution to this problem, allowing Cannabis growers to control the infection at its delicate growing stages. Tissue culture has the potential to grow all disease-free plants!

What is Tissue Culture?

Tissue culture is a technique in which only a few or single cells are used to regenerate the whole plant. The process utilizes any parts of the plant including leaf, stem, roots, embryo, or seeds to grow into a whole plant. The plant is maintained in a lab environment until all organs are regenerated and then it’s moved to the greenhouse for acclimatization. So, the process of tissue culture commonly involves four steps:

1. Initiation stage: It involves cutting the explant from the source plant, surface sterilizing it, and then placing it on the medium to start callus formation.
2. Multiplication stage: It involves induction of shoot formation from the formed callus. This stage requires cytokinin for the proper development of stems.
3. Rooting Stage: It involves the regeneration of shoots from the shoots. In this stage, auxin is used to induce adventitious roots formation.
4. Acclimatization Stage: In this stage, plantlets are moved to the greenhouse for acclimatization and maintenance before they move to the field.

What are the advantages of Tissue Culture?

1. It allows a large number of plants to grow in a small space.
2. It allows mass production of plants.
3. It helps to grow plants on the verge of extinction or endangered species.
4. It helps to produce disease-free plants.
5. It allows it to produce hybrids of plants or to grow haploid plants.
6. It maintains the genetics of the plant. If you would like to grow a plant only for specific characteristics, you can easily do it by using tissue culture methods.

Can you regenerate a disease-free plant from an infected strain using tissue culture?

Yes, you can do it! However, it's not a good idea to use that plant for your process if the plant is severely damaged by the infection. If you observe any kind of infection, you can immediately proceed with the process of tissue culture to get rid of them. You can do this by using the meristem culture or auxiliary node culture technique. One more thing that you can do to avoid infections from spoiling your cultures is by proper surface sterilization of explants and properly removing the dead tissues.

MERISTEM CULTURE TECHNIQUE 

Meristems are undifferentiated cells with the capability to divide throughout life. They are located in several plant organs including root (root apical meristem) and shoot (shoot apical meristem). Based on their location, they are categorized into three groups: apical meristem, intercalary meristem, and Lateral meristem. Why shall you use meristem? Meristems have the capability to differentiate into different other tissues and also because they are undifferentiated, it makes them a stranger to attacking contaminants including viruses. They take time to infect plants. And, because meristematic tissues are themselves free from any contaminants, they are considered safe explants for tissue culture processes. And that's how they help culturists to eliminate viruses from their chosen strain and produce disease-free plants.

The majority of meristem cultures are essentially shoot-tip cultures. One more point to be noted is that different purposes of tissue culture require different sizes of nodal explants. The only exception where the size of the explant is out of concern is the process of micropropagation. The shoot tips are cut into fine pieces to obtain more than one plantlet from each shoot tip. After this, the explants are transferred to Murashige & Skoog media (for the majority of species). To remove endophytic contaminants you can use fungicides or antibiotics.

ARE ANTIBIOTICS HEALTHY?

You may also be aware that antibiotics are not good for the health of tissue culture plants. They negatively impact the growth of plants and also alters their genome. So, what should one do in this case? The best alternative to antibiotics and fungicides is the Plant Preservative Mixture (PPM). It’s an all-rounder player when it comes to avoiding contaminants from cultures. It can prevent any contaminant whether it’s airborne, waterborne, endophyte, or came through human contact. You only require 1-2 ml of PPM per liter of growth media.

So, to summarize you just have to do these three things if your strain is infected and you want to regenerate the plant:

1. Use meristem culture technique to obtain disease-free plants.
2. Perform proper surface sterilization of explants and remove all dead and damaged tissues.
3. Use PPM in your culture media to avoid any type of contaminants from spoiling your cultures.

References

1. https://www.sciencedirect.com/topics/immunology-an...
2. https://www.plantcelltechnology.com/blog/meristem-...
3. https://www.plantcelltechnology.com/pct-blog/advan...
4. https://www.biotech.iastate.edu/publications/lab_p...