The effects on phenotypic traits of rice differed between the two semidwarf genes (sd1 and d60) and also between sd1 loci of different origins (Jukkoku_sd1 and IR8_sd1). The effect on culm length was more pronounced in plants carrying d60 than in those carrying sd1 (culm length: Jukkoku_sd1, 71.8 cm; IR8_sd1, 68.5 cm; and d60, 65.7 cm). The reduction in internode intervals was relatively uniform in lines carrying Jukkoku_sd1 or d60 (uniform reduction type), while reductions of the third and lower intervals were larger than in the upper intervals in lines carrying IR8_sd1 (Figure 3 and Table 1). Thus, the center of gravity will be lower in the lower internode reduction type, suggesting higher lodging resistance in lines carrying IR8_sd1 than in those carrying Jukkoku_sd1 or d60. Although the function of d60 is not known, it is clearly distinct from that of sd1, as the additive double-dwarf effect of sd1 and d60 appeared in Jukkoku_sd1 plus d60 and IR8_sd1 plus d60, respectively. The results of this study demonstrated that d60 has a stronger effect than sd1 on culm length and exerts similar effects on other phenotypic traits as with sd1. Although many semidwarf genes are associated with a reduction in panicle length, d60 does not exert such negative effects on phenotypic traits of rice plants. Taken together, these results showed that d60 is useful for adding genetic diversity to semidwarf varieties and is thus of particular importance in the field of plant bleeding.