Effects of seed tuber size on dormancy and growth characteristics in potato double cropping

Potato (Solanum tuberosum L.) cultivation in double-cropping systems requires planting whole seed tubers of cultivars with a short dormant period (50–70 days). We used the cultivar ‘Saebong’ to determine the ideal seed tuber size for double-cropping. Whole tubers were categorized as small (10–20 g), medium (30–40 g), and large (50–60 g), and their dormancy characteristics were assessed at six dormancy stages. As seed tuber size increased, the dormancy period decreased and the sprouting rate of tubers increased. Plant hormone content analysis showed that abscisic acid (ABA) levels were negatively correlated with tuber size throughout dormancy. In contrast, gibberellin (GA3) and zeatin levels were positively correlated with tuber size during sprouting, suggesting that the faster dormancy release in larger tubers is due to lower ABA during dormancy and higher GA3 and zeatin during sprouting. Additionally, we examined tuber quality and yield characteristics using the same tuber size categories. Medium and large tubers showed higher sprouting rates, more eyes per tuber, higher starch content, and longer sprouts than those of small tubers. Moreover, our field test showed that the sprouts of medium and large tubers emerged earlier than sprouts of small tubers, resulting in longer stems and a higher ground cover rate. Medium and large seed tubers produced 4.30–4.70-fold greater marketable yields than small tubers. Thus, medium and large whole seed tubers are ideal for double cropping, and larger seed tubers exhibit faster dormancy release than their smaller counterparts.