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Micropropagation is a technique that is used to aid in propagating or cloning a particular genotype in the laboratory.
It is generally accepted that there exist many ways that organisms are able to create similar copies of themselves. An excellent example is binary fission, which allows bacteria to divide, and then give birth to daughter cells that are similar in appearance to their parent.
On the other side cuttings (from parents with desirable traits) are employed in botany and agriculture and other fields, for reproducing plants with characteristics similar in comparison to the original plant.
While these techniques result in the creation of individuals with identical features (genotype) in comparison to the plant or organism that originated them, They differ from micropropagation because micropropagation is specifically about the growth of cells or tissues of a specific plant or organism under sterility in a culture.
Although this method is more sophisticated than others employed in cloning, it permits the reproduction of a huge variety of plants within the shortest amount of time.
A few of the plants that are propagated via micropropagation include: Pine Tomatoes, rubber tree, Yam Oil palm Jojoba, Banana.
- In micropropagation, a tiny portion of tissue from plants (e.g. from the apical region or the plant’s the flower or leaves, etc.) can be used to grow many plants.
- Following the preparation of tissue, The first step in micropropagation is called tissue culture, where the tiny tissue is placed in the form of a plate (with the right medium).
- The media that are used in this article are: Linsmaier and Skoog, White’s Medium, Gamborg medium, Nitsch and Nitsch
- Tissue culture is crucial in micropropagation as it’s used to produce small cells and tissues. In this case, the medium supplies all the nutrients and substances (e.g. hormones) that cells require to multiply and develop the root and shoot. Thus, tissue culture is among the most essential aspects of micropropagation.
Methods of Micropropagation
This artificial method of making plantlets is based on five methods:
- Meristem Culture: In this type of micropropagation, a subtending leaf’s primordial and a meristem is inserted into the appropriate growth culture media and left to develop. After a few days, a root plantlet will be produced. When they attain an adequate height, these plantlets are transplanted to the soil. By this process, plants that are disease-free are created and are a great option for the rapid growth of many herbaceous plants.
- Callus Culture: In this technique, the selected plants are placed in an artificial growth medium until the callus develops. After the callus has formed and then they are placed into an environment that is enriched with plants growth regulators to aid in the development of new organs. After a couple of weeks, the plantlet is slowly exposed to the environment.
- Suspension Culture: In this type of micropropagation, the cells or groups that contain cells, are distributed, and let to grow in an aerated, sterile liquid medium for culture.
- Embryo Culture: In the process of embryo-culture the embryo is taken and put into a medium, which is fed with the proper nutrients in an the condition of aseptic.
- Protoplast Culture: In this method, it is possible to isolate the cell of the plant, then culture in a suitable medium to restructure its cell walls and create a callus. In the next step, under appropriate conditions, the cells develop the cell wall. This is which is followed by an increase in cell division and cell differentiation. It then develops into the new plant.
Stages of Micropropagation/Steps of Micropropagation
While micropropagation is usually divided into four major phases, there is the preparatory stage, which occurs prior to any of the other steps. To simplify the process, the entire process could be broken down into five (5) principal steps. This includes:
|Selection of an explant
|Culture initiation and establishment
|Rooting of the shoots
|Transfer of plantlets in the greenhouse environment
Stage 0: Preparative stage
Also called”the mother plant selection stage, stage 0 is an essential stage of micropropagation, which allows for the perfect plant (with desired traits) to be identified and ready to be used in the following stage.
It could mean selecting the right plant, and then allow it to grow under an environment that is clean. Pretreatment can also reduce the chance of contamination.
Based on the plant, One of the methods employed here is to grow your plant inside a greenhouse in certain conditions that are required from the plants. Additionally, certain species like Cordyline spp can be sterilized and foliated (surface sterilization) in this stage. Other strategies used to make sure that the plant is clean in the coming stages include:
- The use of trickle irrigation – unlike overhead irrigation, it reduces the risk of spreading infection (bacteria and fungi).
- The temperature should be maintained at around 25 ° C with a relative humidity of 70% – This can vary dependent on the type of plant.
- The application of thermotherapy (using the power of heat) to kill virus.
The main purpose of Stage 0 is to take care of the plant, and consequently get a starting material which is safe and adapting to the demands of life.
Stage 1: Initiation of Culture
The micropropagation stage is used to ensure a stable beginning by creating the culture of the plant chosen.
Although it’s the second of the five primary micropropagation stages This stage can be broken down in three (3) principal steps that comprise:
1. Cutting a piece of tissue
The first step of this phase is cutting tiny pieces of part of the stem. While some flowers and leaves are employed, using the apical portion and an additional buds is usually suggested. This is due to the fact that, compared to other areas of the plant the apical portion and the additional buds tend to be less susceptible to contamination. In this case, cutting off a tiny portion of the plant is recommended to reduce the possibility of contamination.
- The next step involves disinfecting the tissue of plants. This is a crucial step since the tissue must be sterilized prior to it being able to be used in a culture.
- This process involves washing the plant’s tissue with water. After that, the tissue will be put in ethanol at 95 percent for a short time before being placed in around 1 percent mercuric-chloride and detergent for approximately three minutes.
- Very little of this detergent can be utilizedin the process, e.g. two drops of detergent per 100 ml solution. After three minutes the tissue is washed with the water (autoclaved water) and then placed in sodium hypochlorite along with the smallest amount of detergent for around 10 minutes. With water, the tissue is washed once more to remove the detergent.
- If there is a laminar flow hood accessible, this process is possible to be performed inside the hood in order to improve the final result.
- The process of disinfection helps get rid of any surface contamination.
3. Growing the tissue in the appropriate medium
- The final step in stage 2 is to place the tissues into the proper medium, also called the induction medium. One of the common media utilized for this is Murashige or Skoog medium. However, any medium that is nutrient utilized should have growth hormones and the necessary nutrients to allow the tissue to begin growing.
- In general, the majority of substances used are known to comprise one-half ( half ) strength LePoivre basal salt mix austenite 3 percent sucrose 5 mg/L benzylaminopurine as well being 0.8 percent agar that has pH of 5.7.
- The part of the plant that is cut to make the purpose of culture (e.g. the apical bud or axillary) is referred to as an explant.
- The cells of the apical region are constantly growing and this is one of the reasons why the apical tissue is suitable for cultivation.
- In culture, the nutrients enable cells to divide, and form a massive mass of cells, referred to as the callus.
- Due to the fact that cell proliferation is high during the stage I phase results in the development of a callus. This provides an chance to increase the amount of plantslets.
- Depending on the quantity of plantlets needed depending on the number of plantlets required, the callus may be cut into smaller pieces (making sure not to create any contamination) that are then cultivated in a culture.
- Since several components are derived from the same plant, it is likely that the plantlets all exhibit the same traits.
Stage II – Multiplication stage
- This third phase of micropropagation characterised by the growth of the plant that leads to the development of the shoot. To stimulate growth and an extension of the vegetative shoot (from an elongated callus/mass of cells) the right mix of cytokinins and auxins is utilized.
- Particularly the case of the cytokinin (e.g. Kinetin) that regulates plant growth, aids in the growth of the shoot, and its lengthening from the cell mass in the culture.
Stage III: Shoot elongation and root development
- When micropropagation is in its initial stage the shoot continues to grow within the culture. Furthermore, this is also the time where roots are stimulated to grow. At this point, the plant tissue has produced a small shoot. However, certain roots are still not fully developed.
- This is why auxins are utilized to encourage the development of roots, which helps prepare the plant for planting – Auxins are a kind of growth regulator for plants that aids in the growth of the plant. This includes the growth of different plants like the roots.
- In this instance, it’s worth mentioning that for certain species (e.g. herbaceous species) roots are rapidly created in the cultivation so the use of hormone (auxin) is not required.
Stage IV: Acclimatization (transplantation)
- After the stage of rooting after which the plant is at the point of being planted in soil to continue to grow. However, it usually involves growing the plant under greenhouse conditions so that it can be able to adapt (acclimatization ). A greenhouse is a great option for providing plants with all the environment that it requires for continued growth.
- Transferring plantlets from tissue culture into soil is exposing the plant different conditions. In addition, unlike conditions found in a culture container the plant is at a greater chance of contracting an infection after the plants are placed in soil.
- Since the majority of plants that are grown in cultivation do not have cuticles, allowing them to grow in greenhouse conditions can be beneficial as it helps them prepare for the possibility of shifting temperatures and light intensity which could otherwise cause them to dry out.
- After the period of acclimatization under greenhouse conditions, plantlets are then able to be transplanted to the gardens or farms to allow them to continue in their growth and development.
Advantages of Micropropagation
The technique of micropropagation has proven to be beneficial in a variety of ways. The following are the benefits of micropropagation in plant production
- This is a different method for vegetative propagation that has a greater multiplication rate.
- A large number of similar plants can be extracted from one plant tissue in a brief time.
- Shoot multiplication is one very brief cycle and each cycle is an exponential increase in shootings.
- The tiny-sized prolules are able to be stored and transported quickly.
- The germplasm stock can be kept for many years by this method.
- It assists in the development and maintenance of plant varieties that are pathogen-free.
- In a dioecious species the seed progeny yield is 50 % male and 50 percent female. This technique helps in getting the desired sex for the plant.
- The millions of plantlets that can be kept in culture vials.
- The uniformity of genetic propagules can be maintained with this method.
- It’s an economical process.
- The new species may be propagated.
- Space is a requirement that requires less in addition to human capital.
- This method is not dependent on the time of year and can be implemented at any time.
- Helps to regenerate gene-modified cells following protoplast fusion.
- Most often, it produce healthier plants, which leads to faster growth when compared with the plants grown using an old-fashioned method.
Disadvantages of Micropropagation
Micropropagation may not be the most efficient method for growing plants. The conditions that limit its application include:
- The cost of labor could comprise between 50 and 69 percent of operating expenses.
- A monoculture is created following micropropagation. This results in the absence of general resistance to disease since the progeny plants are all susceptible to the same diseases.
- A plant that is infected may produce infected progeny. This is rare as plant stock is carefully checked and vetted to avoid the culturing of plants with viruses or fungus.
- It is not possible for all plants to be successfully cultivated in tissue typically because the ideal growing medium is not established or the plants release other metabolic compounds that hinder or cause death to the plant.
- Sometimes, plants or cultivars don’t conform to form after being cultivated. This can be due to the kind of substance used in the initial phase, or due to the longevity of the propagule or cell line.
- Some plants are difficult to cleanse from fungal harmful organisms.
The main drawback in the application of micropropagation in several plants is the expense of production. For many species, seedsthat are typically disease-free and produce in large quantities, can produce plants (see the orthodox seed) in good numbers and at an affordable cost. Because of this, most plant breeders don’t use micropropagation as the expense is too high. Some breeders utilize it to grow stocks that can be utilized for seed multiplication.
The process’s automation could decrease the cost of labour, but isn’t easy to attain despite efforts to find technological solutions.
Important Points of Micropropagation
- It’s the propagation of plants through the growth of plantlets in tissue culture before planting it.
- It aids in producing plants that exhibit desirable characteristics.
- It is a gradual process that results in a huge number of plants being created from one explant.
- The plants that are produced can be genetically similar to those of the mother plant.
- The plants are created through the following steps: setting up the plant, the multiplication of the explant within a culture medium, the transfer of the growing shoots to a medium that allows for growth, and finally, placing the plant into the soil to encourage root growth, and permitting the development and growth of the plant under optimal conditions.