Question

Describe the main procedures available for the micropropagation of plants, and discuss their application to potato production.

Answer 1

The part of the plant which is used for culturing is called as explants. These explants are cultured in-vitro on a nutrient medium which fulfills its nutritional requirements. The medium must have the following essentiality

Macronutrients – Which include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S) required for well defined growth and morphogenesis.
Micronutrients – iron (Fe), manganese (Mn), zinc (Zn) crucial for the growth of tissues.
Energy source – one of the most important content of the nutrient media. Sucrose is the widely used carbon source which provide C, H, and O, Vitamins, amino acids, and many inorganic salts.

Apart the culture media acts as a medium for providing phytohormones or plant growth regulators to the tissues to bring the morphogenesis as required. The explants tissues first lose their specificity to change into a hard brown lump termed as callus. This callus then splits to form a plant organ or a whole new plant which depends totally upon the quantity as well as the composition of phytohormones supplied.

Callus culture

Callus is a undifferentiated mass of parenchymatous cells. As and when a living plant tissue is put in an artificial growing medium having other conditions favorable as well, callus is formed. The callus growth varies with the different homogenous levels of auxin and Cyotkininn. The callus growth and its embryogenesis can be defined into three different stages.

A) Fast production of callus when placing the explants in culture medium.
B) The callus is moved to other medium which contain growth regulators for the induction of adventitious organs.
C) Thereupon the new plantlet is exposed gradually to the environmental condition.

Suspension

suspension culture which is refered to cells and or groups of cells dispersed and growing in an aerated liquid culture medium is put in a liquid medium and shaken vigorously with a balanced dose of hormones.

Embryo culture

The embryo is put in a culture medium having proper nutrient in aseptic condition. So as to get quick and optimised growth into plantlets, it is transferred to soil.

Protoplast culture

The plant cell can be isolated with the aid of wall degrading enzyme. The growth initiated in a suitable culture medium under controlled condition for regeneration of plantlets, the protoplast forms a cell wall which is followed by an increase in cell division and differentiation.

Tissue culture helps in a very rapid propagation. In traditional propagation, one tuber forms approximately 8 daughter tubers in one growing season but in tissue culture 100,000 identical plantlets can be formed in eight months which when transferred to the field, can produce 50 MT of potatoes.

Each plant has a root system, leaves and growth points. Apical meristem is found at the apex of a potato stem having lateral growth points. These buds have a meristem which helps it to form a different plant.

The method of this technique is simple. plantlets are disease free and grown in test tubes on a nutrient media. plantlets are cut into 3 to 10 nodal sections after a gap of 18-60 days. Every cutting is planted in a new test tube. This is repeated until the desired number of plantlets is obtained which are then separated from the tubes and grown in sterile soil.