Gibberellic Acid and Ethephon Alter Potato Minituber Bud Dormancy and Improve Seed Tuber Yield

While greenhouse production of minitubers has markedly improved production of disease free seed, minituber dormancy can be an issue. This study tested application of abscisic acid (ABA), ethylene (E), gibberellic acid (GA) and the combination of E+GA on release of dormancy in potato minitubers, sprout development, and subsequent effects on field plant growth and yield of seed tubers. Cultivars were categorized on the basis of known dormancy responses as follows: (1) one short dormancy cultivar, Silverton Russet, (2) three intermediate dormancy cultivars, Russet Norkotah (RNK), Sangre S-14 and Desiree, and (3) two long dormancy cultivars, Nooksack and Russet Norkotah Selection 3 (RNK-S3). Eighty eight to 93% of E+GA treated minitubers from cultivars in the long dormancy group developed sprouts signaling the end of dormancy within 5 weeks, while the control and ABA treated minitubers were totally dormant with 0% bud break. With the intermediate cultivars E+GA treated minitubers had 100% bud break compared to 37 to 55% bud break in the control minitubers. Treated long dormant minitubers also had 2.1 to 2.5 more sprouts per minituber and 1.6 to 2.4 cm longer sprouts. E+GA treated minitubers planted in field plot trials produced mature plants that were 19 to 36 cm per plant taller, with up to 3.9 to 8.8 more seed tubers per plant, and 1.9 to 4.2 kg per plot higher yields. The laboratory protocol developed to predict dormancy breaking attributes provided a reasonable estimate of cultivar dormancy under field conditions.