Abstract
Potato microtubers (MT), generally 1 gram fresh weight, are mass-produced under in-vitro conditions, and they are used as seed tubers in the fields. We previously found the varietal differences in tuber yield characters of plants grown from MT, and the varieties were divided into two groups; one with a larger number of tubers with lighter individual tuber weight than in plants from conventional seed tubers (CT) (tuber-number type), and the other with opposite characters (tuber-weight type). The purpose of this study is to make clear the mechanism of regulating the yield characters of MT plants. We conducted experiments using four varieties, including different types of the yield characters in MT plants, for five years. In all five years, the MT/CT ratio in tuber number was negatively correlated with that in individual tuber weight. The number of tubers increased from an early tuber growth stage to a harvest time was larger in MT plants of tuber-number type varieties than in that of tuber-weight type varieties. There was a significant negative correlation between the increased number of tubers and the tuber yield at an early tuber growth stage. These results suggest that tuber growth may affect earliness or lateness of the end of tuber formation. The findings of the characteristics of varieties found in this study may be useful to improve the multiplication rates of the seed potato production using MT plants.
