Viviparous Characteristics of Four Korean japonica Rice Cultivars Adapted to Tropical Region.

Viviparous germination (VG) often occurs in high temperature and humidity or continuous rains and results in reduced grain quality and yield. Usually, japonica rice cultivars had higher VG than those of indica rice cultivars. VG is likely to be higher in the humid tropics. This study carried out to evaluate pre-harvest sprouting (PHS) characteristics of four Korean japonica rice cultivars, MS11, Japonica1, Japonica2 and Jinmi, which were developed in order to be adapted to tropical region. One Tongil type rice cultivar, Saegyejinmi and one indica rice cultivar, IR72 were used as check variety. We examined the viviparous germination rate (VGR) using the panicles at 40 days after first heading in growth chamber and field condition at International Rice Research Institute, the Philippines and National Institute of Crop Science, Korea, respectively. As results, VGR of japonica rice cultivar was higher than that of Tongil-type and indica rice cultivar and that of MS11, Japonica1 were lower than that of Jinmi, parent of former two rice cultivar, meaning that it has more improved than its parent. In particular, among japonica rice cultivar, VGR of MS11 was the lowest both in temperate and tropical regions and that of Japonica2 was the highest both areas. However, VG tolerance of those cultivars raised, VGR of tolerant two was still higher than that of indica cultivar. These results showed that in terms of viviparity, PHS tolerant MS11 and Japonica1 were suitable for but Japonica2 was inappropriate to cultivation in the tropical regions. Furthermore, it is necessary to improve VG tolerance of japonica rice cultivar to better adapt to tropical region.