Production of elite minitubers of potato
2003
Majidi, Eslam | Davoodi, Daryoush
Vegetatively propagated plants such as the potato are capable of passing viral diseases from one vegetative generation to the next. Advances in potato tissue culture permit the in vitro maintenance of commercial varieties and/or experimental breeding clones for use as seedstocks. These in vitro methods can also be used for producing pathogen-free stocks from plants systematically infected with pathogens such as bacteria, mycoplasms, fungi and viruses. However, the presence of viruses in the plants can reduce the yield and/or quality of the crop.Yield increases up to 300% (averaging 30%) have been reported following replacement of virus-infected stock with specific pathogen-free plants. There are approximately 23 virus and virus-like organisms which cause disease in the potato. Since the 1960&rsquos, heat therapy and meristem-tip culture have been used to eliminate viruses from the potato. The success of the meristem-tip culture is judged by the percentage of plantlet regeneration and eradication of viruses (7). To obtain a high yield of virus-free plantlets the following factors should be taken into account: 1)meristem size, 2)culture media, 3)effect of thermotherapy and/or chemotherapy, and 4)in vitro growing conditions. The present investigation was carried out to determine efficiency of in vitro bioreactor-based tuberization of potato. In vitro potato stock plants (Solanum tuberosum L. CV. Agria) were obtained from apical meristems followed by thermotherapy. These in vitro plants were multiplied by serial subcultures in 300 ml jars containing MS liquid medium. Cultures were incubated under 24/22℃day/night temperature regime with a 16-h photoperiod fluorescent light at an irradiance of 3000 lux (36 μmol m-2 s-1). Multiplication medium consisted of MS salts and vitamins, 30 gL-1 sucrose, 2 mgL-1 6-benzylaminopurine (BAP), 0.1 mgL-1 naphthalene acetic acid (NAA) and 1.0 mgL-1 gibberellic acid (GA3). Tuber induction medium was the same as basal medium except 80 g L-1 sucrose, and 7 mg L-1 BAP were used. Shoots produced in a 300ml jar were transplanted into a 3L bioreactor vessel and the medium was pumped into it every 8 hrs. to immerse the shoots for about 30 minutes. The entire medium was changed with tuber induction liquid medium after 4 weeks. These cultures were incubated under continuous dark condition at 20℃for 4 weeks. The growing shoots were subcultured from 300ml jar to bioreactor in which they continue to grow. After 3 days tuber induction was observed. The tuberization occurred mainly at middle part of the bioreactor. The total number of microtubers in this 3L bioreactor was about 550 and was very more efficient than routine system (3 to 4 microtubers per 300 ml jar).
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