Micropropagation is simply called as propagation technique of plants through vegetative parts which is also known as cloning or clonal propagation. For this technique, any part of plant that may be cell or tissue is placed in artificial nutrient medium i.e. MS medium which is free from microorganisms (sterilized condition) and in laboratory / controlled condition where complete new plant is grown or cultured from it.
Generally, for the successful propagation through this technique, initially small plant part that may be tissue or cell which is defined as explant is taken which is cultured in artificial nutrient medium. From this process, an undifferentiated mass of tissue known as callus is formed after keeping them in sterilized incubator. Now, through this explant culture either it is grown to prepare callus initially and again further sub cultured to grow plants or directly plants are grown from explant avoiding the process between them which is dependent on quantity of plant growth hormone kept in artificial nutrient medium. When 2,4 D – auxin (Dichlorophenoxy acetic acid) & kinetin is used as plant growth hormone in nutrient medium, there is high possibility of formation of callus but when Benzyl amino purine (cytokinin) and Napthalene acetic acid (NAA – auxin) are kept in nutrient medium there will be high possibility of plantlet formation.
Callus, formed after by use of this technique can be cut into smaller pieces and such pieces when placed in growing artificial nutrient medium in sterilized condition, shoot emergence takes place from that cut and for rooting in that newly emerged shoot, they are transplanted in medium placed with rooting hormone (auxin). Eventually, roots are developed inside the culture medium i.e. glass vessels to form tiny juvenile plantlets. When plantlets are formed again explant is taken from such tiny juvenile plantlets for further culture to grow numerous plants from them. This process is now called as sub culture. On the other hand, such tiny juvenile plantlet can be grown in sand at first which is transplanted to vessel after sometimes and when developed to sufficient height & hardiness, it is finally transplanted in the main field.
The following mentioned are the special precautions to be taken while working in tissue culture or micropropagation lab.
- Keep long hair tied back wearing gloves and lab coat properly.
- Clean all the working surface of the lab with ethanol.
- Equipment using in the lab or any procedure should be fully sterilized.
- Labelling of all material before starting and setting up all necessary equipment before work is mandatory.
- Keep tubes, plates or bottles containing useful material closed as much as possible or if you need to open completely place it facing completely upward.
- Inspection of all the required equipment and media is necessary for any observatory contamination before using them.
- Use of proper antibiotics in the media is mandatory.
- Never pass hands or arms over any open plates, bottles and tubes.
- Notation of observations, methods, and results in lab notebook is necessary. UV lamp should be turned on for 10 minutes for sterilizing the working area.
Benefits of Micropropagation:
Micropropagation is very beneficial and advantageous method of propagation with respect to traditional method of propagation. They are briefly mentioned below: –
- Micropropagation helps in production of many plants at single time which are clone of each other identical in characters.
- The most promising benefit of micropropagation is production of disease free (viral, bacterial & fungal) plants in huge amount.
- It is very useful technique in plants which do not produce viable seeds or produce very few seeds in uneconomical way or which do not produce any seeds to propagate seedlings.
- It is only method where regeneration of genetically modified cell is possible.
- This technique had high fecundity rate even in thousands in comparison to conventional method.
- Plants like orchid having very small seeds are grown successfully from seeds in sterile culture.
- Seedlings can be stored in small area for longer duration with high numbers per unit area than other methods.
Disadvantages of Micropropagation:
Micropropagation is not always the perfect method of propagation or multiplying plants or propagules. Apart from several promising advantages and benefits of micropropagation, some negative aspects are also attached to this technique. They are briefly described below: –
- The most disagreeing point of micropropagation is its expensive cost of production of propagules with respect to propagation through seeds.
- Most crops produce viable disease-free seeds for propagation with very low cost of production and micropropagation in these cases is very useless to breeders and farmers.
- This method involves advanced / complex technological arrangement with precise precaution and measurement during work which is very difficult to adapt to people of country like Nepal.
- Similarly, it is much labor-intensive comprising of 70% labor cost only.
- If any infected plant sample is taken, there may be production of thousands of infected propagules causing both production loss & economic loss.
- At some times, propagules do not come true to the type and not every plant can be propagated by this method as proper growth medium of all crops / plants have not been known or plant may produce any secondary metabolite that can either kill or stunt the explant.
- It is very difficult to disinfect the fungal organisms in some plants and all propagules may be infected with same infection at a time because of same identity.
Apart from all these disadvantages of micropropagation, it is very new and advanced method of producing disease free propagules. It can be successful method of raising propagules to make greater profit in near future to the breeders or farmers in Nepal too.