Abstract
The tillering behavior of the semidwarf indica variety IR 36 and japonica-indica hybrid variety Suweon 258 was compared with that of Japanese panicle weight (Koganenishiki) and number (Nakateshinsenbon) type varieties (japonica) under three planting densities (11.1, 22.2 and 44.4 hills m-2) . At the maximum tiller number stage (MTS), the total number of tillers produced by IR 36 and Suweon 258 was about 1.8-2.5 larger than the number produced by Koganenishiki (ranges include all three planting densities), and about 1.1-1.7 larger than the number produced by Nakateshinsenbon. The larger number of tillers of IR 36 and Suweon 258 was due to the higher production of tillers of each order, except for the tertiary tillers in the high density planting. The percentage of secondary tillers at each of the planting densities and that of the tertiary tillers in the low density planting were higher in IR 36 and Suweon 258 than in the Japanese varieties. At the harvesting stage, the total number of tiller or that of tillers of each order in IR 36 and Suweon 258 were compared with those of Koganenishiki and Nakateshinsenbon, respectively, due to the considerable difference in the percentage of productive tillers. The percentage of productive tillers to the total number of tillers and that of the tillers of each order, especially the secondary tillers, decreased with increasing planting densities in all the varieties. However, the percentages for IR 36 and Suweon 258 were lower than those of the Japanese varieties, regardless of the planting density. The lower percentage of productive tillers of IR 36 and Suweon 258 was mainly attributed to the higher percentage of shorter tillers (lower than 70% of the main stem length at MTS) in tillers of each order.
