The days to heading were compared (Figure 2). The earliness of varieties of Koshihikari and donors of semidwarf genes is as follows: Koshihikari, an early-medium maturing variety; Jukkoku, a medium-late maturing variety; Kinuhikari, an early-medium maturing variety; and Hokuriku 100, an early-medium maturing variety. The heading panicles were observed first in Koshihikari carrying IR8_sd1 (83 days to heading) and the latest heading panicles were observed in Koshihikari carrying Jukkoku_sd1 or Jukkoku_sd1 plus d60 (93 days to heading). However, the difference in the average number of days to heading was the largest between lines carrying IR8_sd1 (86.5 days) and those carrying d60 (90.5 days), but this 4-day difference was thought to be minor (Figure 2). Thus, it was concluded that the time required for maturing was comparable among lines and the differences in traits, such as panicle length, were attributed to genetic factors.