The mean values of the individual traits in plants of each genotype were calculated and the percent differences relative to the corresponding mean values of Koshihikari were compared. Introduction of a semidwarf gene (or genes) resulted in a reduction in culm length. The mean culm length of Koshihikari was 88.8 cm, while those of lines carrying Jukkoku_sd1, IR8_sd1, d60, Jukkoku_sd1 plus d60, and IR8_sd1 plus d60 were 71.8, 68.5, 65.7, 48.6, and 50.2 cm, respectively (Table 1 and Figure 3). Similarly, internode intervals were also reduced by the introduction of at least one semidwarf gene. While reductions in internode intervals were relatively uniform in lines carrying Jukkoku_sd1 (23.9%, 27.5%, 27.0%, 23.3%, and 19.4%: percent difference, from upper to lower internode intervals), the reduction in length between the third and fourth and between the fourth and fifth internodes was markedly large in lines carrying IR8_sd1 (16.4%, 31.5%, 37.0%, 42.6%, and 45.0%: percent difference, from upper to lower internode intervals). Reductions in internode intervals were relatively uniform in lines carrying d60 (24.2%, 32.6%, 27.4%, 34.5%, and 45.7%: percent difference, from upper to lower internode intervals), while percent differences were larger than those observed in lines carrying Jukkoku_sd1. In the sd1 plus d60 lines, marked reductions were observed in length between neighboring internodes, probably attributed to the additive effect of sd1 and d60 (Table 1 and Figure 3). The interval between the fourth and fifth internodes often disappeared in plants carrying IR8-sd1 and in sd1 plus d60 lines, which showed a marked reduction in length between the lower internodes.