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ABSTRACT

Potato production is often exposed to vagaries of pests and diseases and the rate of infection of potato seed tubers increases over the years. Due to transboundary exchange of potato planting stock, there is a huge risk of spreading diseases. Micropropagation of potato and subsequent microtuberization under in vitro conditions has solution to provide disease free materials that can be used for seed tuber production programmes and germplasm conservation with minimal risk for cultivation and trade of this important food crop.

Keywords: Potato, Meristem culture, microtubers, germplasm

 

Potato (Solanum tuberosum L.) is a commercial vegetable crop generally propagated by vegetative means using tubers. Potatoes are often prone to pests and diseases limiting the production. Preventing the infection of pathogen during the propagation is an important step to ensure supply of quality planting materials to farmers or scientists involved in germplasm conservation. Virus free potato plants can be produced by adopting in vitro techniques like meristem culture. Microtubers gain significance with its multiple applications in propagation, storage and transport (Mamiya et al., 2020).

Microtubers of potato are smaller in size, produced by tissue culture (Donnelly et al. 2003) and are easy to handle than in vitro plants. These tubers can be easily stored under protected conditions for several months and can be planted directly in the field. Microtubers are essential component of potato seed production. These microtubers can be produced either by agar-gelled or liquid medium. Liquid medium is favoured over solid media, as it is amenable for scaling up by automated production using bioreactors that has advantages of reduced labor costs and ease of maintenance (McCown and Joyce 1991; Piao et al. 2003).

In vitro tuberization in potato

Potato microtubers produced under in vitro conditions has significant advantages of year round production of tubers which are disease free and can be easily stored and transported. Seed production programme of potato can be envisaged either through in vitro multiplication and plantlet regeneration or microtuber production from shoots (Naik and Karihaloo, 2007). The scheme for microtuberization is presented in Fig.1.

Microtuber production procedure consists of

a)          mass multiplication of in vitro plantlets

b)          microtuber production

c)          harvesting and storage

a)    Mass multiplication of in vitro plantlets

•  Liquid cultures are preferred for mass propagation that can be established at a pilot scale in a 250 mL Erlenmeyer flasks or magenta boxes using the sterile propagation media described above excluding the addition of agar.

•  About 10-12 stem segments, each with 3-4 nodes can be inoculated in each flask/box

•  The inoculated cultures are incubated at the conditions described above. Care has to be taken to prevent the submergence of the explants in the liquid medium. Rafts/paper bridges can be made inside the culture vessels to support the explants.

•  In about 20-25 days, all the axillary buds grow into full plants and fill the containers

 b)    Microtuber production

•  After three weeks of propagation in liquid cultures, the liquid propagation medium is decanted and the microtuber induction medium is filled.

•  The standardized microtuber induction medium is based on the MS salts supplemented with 10 mg/L BAP, 500 mg/L chlorocholine chloride (CCC) and 80 g/L of sucrose. High sucrose favours starchy tuber formation.

•  The microtubers are induced under complete darkness at 20 °C within 8-10 days from the axillary ends of the shoots. Depending on the genotypes shoots will be ready for harvest in 60-90 days.

•  On an average, 15-20 microtubers of weight 100-150 mg are produced in each flask or magenta box.

c. Harvesting and storage of microtubers

•  Prior to harvest of the microtubers, greening is done by exposing induction cultures to white fluorescent lights or diffused sunlight for 10-15 days.

•  The green microtubers are harvested in plastic trays without causing any damage and washed.

•  For ease of storage and getting rid of contaminants by microbes, the microtubers are treated with fungicide (mancozeb 78% WP @ 0.2%) for 10 min. and allowed to dry in the dark at 20 °C for 2 days. 

•  The dried microtubers are packed in perforated polybags and stored at 5 °C for 4-5 months under dark to break the dormancy.

•  The microtubers are ready for sprouting and field planting in about 3-4 months of storage.

Conclusion

                Micropropagation in potato for quality plant material generation through mericloning when coupled with extended procedures for microtuberization has greater advantages in quality seed production and germplasm conservation. Microtubers of potato offer easy handling, storage operations without any specialized infrastructures and transport of germplasm.

 

References

Donnelly, D.J, Coleman, W.K., and Coleman, S.E. (2003). Potato microtuber production and performance: A review. American Journal of Potato Research 80: 103–115

Mamiya, K., Tanabe, K., and Onishi, N. (2020). Production of potato (Solanum tuberosum, L.) microtubers using plastic culture bags. Plant biotechnology (Tokyo, Japan), 37(2), 233–238.

McCown, B.H., and Joyce, P.J. (1991). Automated propagation of microtubers of potato. In: Vasil IK (ed.) Scale-Up and Automation in Plant Propagation. Academic Press, San Diego, pp 95–110

Naik, P.S., and Karihaloo, J.L. (2007). Micropropagation for Production of Quality Potato Seed in Asia-Pacific. Asia-Pacific Consortium on Agricultural Biotechnology, New Delhi, India. 54 P.

 

Piao, X.C., Chakrabarty, D., Hahn, E.J., and Paek, K.Y. (2003). A simple method for mass production of potato microtubers using a bioreactor system. Current Science 84: 1129–1132.

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3. Microtuberization in potato-revised_compressed.pdf