In order to -use microtubers as seed potatoes, microtubers should better be uniformly-sized, mass-produced, and easily adapted to field conditions of less favorable environment. This study was conducted to increase production rate of microtubers of Daiji, Sumi, and Namjak potatoes with regard to plantlet culture conditions and periods, the levels of MS vitamines in plantlet culture.
Plantlet growth was partly affected by temperature and day-length during plantlet culture. No difference in plantlet growth was observed at 20 and 25℃, but the growth was slightly reduced at 16℃ with Sumi. Plantlet growth was better at 16 and 20℃ than at 25℃ with Daiji. Longer day-length increased plantlet growth of Sumi while it did not affect the growth of Daiji.
Temperature during plantlet culture influenced in vitro microtuberization of potatoes. Better microtuberization was observed at 20℃, followed by 25℃, and 16℃ with Sumi, while 20℃ was favorable followed by 16v, and 25℃ with Daiji. However, day-length during plantlet culture did not affect microtuberization in both cultivars.
In Daiji potato, the plantlets grown in PC-3 medium combined with GAS, kinetin and 100 times strength of vitamines of MS basic medium resulted in larger microtubers and shorter T_(50) (days needed for 50% plantlets to tuberize) than those grown in PC-2 medium combined with GA₃ and kinetin.
In Daiji potato, the TI-5 medium combined with 9% sucrose promoted tuberization and increased microtuber weight compared with the TI-3 combined with 6% sucrose, BAP and CCC.
Better plantlet growth and more lateral shoots per plantlet were obtained as plantlet culture period increased up to eight weeks. With Namjak plantlet growth rate was significantly reduced between six and eight weeks. Plantlet growth was slightly increased at 20 than at 25℃.
More and bigger microtubers were produced from plantlets grown for eight weeks in liquid than in solid medium. Microplantlets grown at 20℃ produced more but smaller tubers compared with those at 25℃. The optimum culture period was eight weeks for Daiji and six or eight weeks for Namjak.
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