Kiichi Hanada

Character Expression of the Semidwarfing Gene sd-1 in Rice (Oryza sativa L.) : II. Appearance and development of tillers

Gene expression in tiller development by the semidwarfing gene sd-1 was studied under two different nitrogen levels. A Japonica tall variety Norin 29, its semidwarfing near isogenic line SC-TN 1, and an Indica variety Taichung Native 1 (TN 1) were used. SC-TN 1 was obtained by transferring the semidwarfing gene sd-1 from TN 1 into Norin 29. The appearance ratio of tillers in TN 1 was larger than that of the two Japonica varieties in primary and secondary tillers at upper nodes. SC-TN 1 had a greater appearance ratio of primary tillers at upper nodes under low nitrogen condition and that of secondary tillers irrespective of nitrogen condition compared with Norin 29. It seems that the semidwarfing gene sd-1 increases the appearance ratio of tillers and promotes the development of tillers. The primary tillers of the two semidwarf varieties tended to reach the age of 1 earlier than those of Norin 29. The age was expressed by the number of leaves whose leaf blade had completely emerged from the leaf sheath of the leaf immediately below it. The varietal difference in the increasing rate of the age of tillers was not always recognized clearly. The relative tiller age of the semidwarf varieties was greater than that of Norin 29, mainly due to the characteristic of reaching the age of 1 at an earlier stage.