Gene effects on the yield performance were compared among promising semidwarf genes, namely, novel gene d60, representative gene sd1 with different two source IR8 and Jukkoku, and double dwarf combinations of d60 with each sd1 allele, in a Koshihikari background. Compared with the culm length of variety Koshihikari (mean, 88.8 cm), that of the semidwarf or double dwarf lines carrying Jukkoku_sd1, IR8_sd1, d60, Jukkoku_sd1 plus d60, or IR8_sd1 plus d60 was shortened to 71.8 cm, 68.5 cm, 65.7 cm, 48.6 cm, and 50.3 cm, respectively. Compared with the yield of Koshihikari (mean, 665.3 g/m2), that of the line carrying Jukkoku_sd1 allele showed the highest value (772.6 g/m2, 16.1% higher than Koshihikari), while that of IR8_sd1, d60 and IR8_sd1 plus d60, was slightly decreased by 7.1%, 5.5%, and 9.7% respectively. The line carrying Jukkoku_sd1 also showed the highest value in number of panicles and florets/panicle, 16.2% and 11.1% higher than in Koshihikari, respectively, and these effects were responsible for the increases in yield. The 1000-grain weight was equivalent among all genetic lines. Except for the semidwarf line carrying Jukkoku_sd1, semidwarf line carrying d60 was equivalent to line carrying IR8_sd1in the yield of unpolished rice, and yield components such as panicle length, panicle number, floret number /panicle. Therefore, the semidwarfing gene d60 is one of the best possible choices in practical breeding.
Keywords: d60; growth; phenotyping; rice; sd1; semidawarf gene; yield component.