Potato microtubers are used as pathogen-tested in vitro stocks for certified seed potato production. Microtubers grown in a rotating bioreactor grew at a faster rate when the medium was replaced frequently. Although the total microtuber number was not affected, the number of microtubers over 1 g quadrupled when 75% of the medium was replaced every 2 weeks when compared with no medium refreshment. Significantly slower microtuber growth rates resulted when a lower sugar concentration (40 g 1-1 instead of 80 g 1-1) was used or when a mixture of glucose and fructose replaced sucrose. Although high sucrose levels are necessary for optimal microtuber production, the sucrose supplied was rapidly hydrolyzed into glucose and fructose, making the long-term maintenance of desirable sucrose levels difficult. These results indicate that successful strategies to reduce sucrose hydrolysis without inhibiting microtuber growth will improve the efficiency of sucrose utilization in potato microtuber bioreactors.
Keywords: In vitro tuberization; Invertase; Key words Solanum tuberosum L.; Micropropagation.