Micropropagation

 

Micropropagation- In vitro propagation

The miniature version of conventional propagation

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Plant tissue culture is used to maintain or grow plant cells by in vitro cultivation under aseptic and controlled environment conditions. In short plant tissue culture is a collection of techniques used for the production of virus-free plants, for the production of artificial seeds and trangenic pants, for the varietal improvements of plants, and many more.

In other terms, it is an experimental technique through which callus ( a mass of cells) is produced from explant cells. Tissue culture refers to the growth of organs, tissues, and cells in an artificial medium.

Gottlieb Haberlandt is considered a father of plant tissue culture because in 1902 he suggested that “ one could successfully cultivate artificial embryos from vegetative cells”.The idea of Totipotency was conceived by him. He was the first to culture isolated, fully differentiated cells in a nutrient medium.

Micropropagation is a modern plant tissue culture methods used to rapidly multiplying stock plant material to produce many progeny plants. It is an essential technique for the plant breeding program. It is the fastest method of asexual reproduction in comparison to propagation through seeds.

One of the most important applications of plant tissue culture is the micropropagation of plant species and it has attained the status of a large plant-based industry.

Micropropagation such a promising technique to obtain genetically pure elite populations under in vitro conditions. This technique is a miniature version of conventional propagation. Micropropagation of plants through tissue culture technique contributed significantly to the enhanced production of high-quality planting material. 

It has now come to stay as an important technique for the rapid production of many commercially important plants like Gladiolus, Eucalyptus, Gerbera, Dalbergia, Freesia, and several important fruit trees and medicinal plants.

Major Steps In micropropagation

1. Selection of healthy disease-free mother plant for culture initiation.
2. Establishment of aseptic culture.
3. Shoot multiplication by using a defined culture medium.
4. Rooting of regenerated shoots in vitro and germination of somatic embryos.
5. Shoots are separated manually from clusters and transferred in a rooting medium.
6. Acclimatization or hardening by transfer of plantlets to the natural environment.

Step 1 -The selection of elite mother plant

This step is the grass root of the micropropagation process. All the methodology and its results depend upon the selection of plant samples for culture initiation. The sample of the plant should be disease-free.

Step 2-Establishment of aseptic culture

After the selection of explant. The trimming process is done. The surface sterilization of explant is important for the establishment of an aseptic condition. Detergents, antioxidants,s and other sterilizing chemicals are used for surface sterilization. After that proper washing process occurs for the removal of sterilizing chemicals adherence. Then establishment it on initial medium.

Step 3-Shoot multiplication

Shoot multiplication can occur in various ways like, from shoot tip and nodal explant, directly from explants, indirect from callus, somatic embryo formation from explant or callus.

Step 4-Rooting 

 For rooting, regenerated shoots are transferred into a rooting medium in vitro conditions and germination of somatic embryos occurs. Then shoots are separated manually from clusters and transferred in a rooting medium containing an auxin or on a medium having low salt concentration or reduced sugar level. 

Step 5- Acclimatization or Hardening 

Transfer of platelets to the natural environment concerns the transfer of plantlets to the soil for hardening under greenhouse conditions. Hardening off plants imparts some tolerance to moisture stress and a shift from heterotrophic to autotrophic nutrition. During hardening, plants are developed cuticle and their stomata start functioning. Hardened plants are then transferred to glass or poly houses with normal environmental conditions. 

Advantages of Micropropagation

1. Allows rapid and large-scale production of desired horticulture varieties.
2. Helps to produce genetically uniform plants i.e. clones and development of genetically transformed plants I,e, transgenics are be produced with the help of this technique.
3. Allow rapid multiplication.
4. Provides a reliable and economical method for maintaining pathogen-free plants.
5. Plant multiplication can continue throughout the year irrespective of seasons.
6. Multiplication of plants can occur in a small space in a tissue culture lab because each flask can accommodate hundreds of plantlets.
7. Micropropagation facilitates the international exchange of germplasm without the inherent risk of spreading diseases and pathogens.
8. Stocks of germplasm can be maintained for many years.
9. Plants with very small seeds like orchids are propagated from seed in sterile culture.
10. Useful to produce sterile plants that do not produce viable seeds.

Micropropagation is true to the type of propagation of selected genotypes using small pieces of tissues that can be used to raise hundreds and thousands of plants in a continuous process.

References : 

Bhojwani, S.S. and Razdan, M.K. 1982.Plant Tissue Culture: Theory and Practice. Elsevier Sci. Publ. Amsterdam .p1–520

NE Borloung, Plant Physiology 124(2),487–490,2000