Modification of potato microtuber dormancy during induction and growth in vitro or ex vitro

Prolonged or highly variable dormancy can be a significant impediment to th e efficient use of potato (Solanum tuberosum L.) microtubers by the seed in dustry. In the present study, reductions in microtuber dormancy duration we re obtained in cultivars commonly used by the processing industry (Kennebec , Russet Burbank and Shepody). This was achieved by modifying microtuber in duction media and applying various dormancy-release treatments after harves t, with or without prior storage. An 8 h photoperiod, instead of continuous darkness during microtuber induction and development, increased microtuber yield while reducing dormancy duration. Dormancy duration was also shorten ed by increased sucrose concentration during microtuber induction under an 8 h photoperiod. As sucrose was increased from 4 to 16% under an 8 h photop eriod, mean dormancy duration decreased by 86 d for Shepody, 65 d for Kenne bec and 46 d for Russet Burbank. During the ex vitro storage period, 24 h t reatment with bromoethane vapor (from 0.22 ml liquid BE per L volume) or br omoethane vapor followed by a 3 d treatment of 60% CO2/ 20% O-2/ 20% N-2 re sulted in a rapid dormancy release of freshly harvested microtubers. These dormancy-releasing treatments significantly increased minituber yields unde r greenhouse conditions for all cultivars when compared to untreated contro ls. Increased minituber yields mere also observed when dormancy release tre atments were applied to microtubers after storage at 6 C for 8 weeks. The r esults demonstrate that microtuber dormancy duration can be manipulated dur ing growth in vitro or ex vitro. However, optimization may require cultivar -specific protocols.