"Gopumbyeo" is a new japonica rice variety developed and registered by the rice breeding team of National Institute of Crop Science, RDA in 2004, which was derived from a cross between a line SR15225-B-22-1-2 which has good eating-quality and high yield potential and a line SR15140-58-2-2-3 which has lodging and disease resistances. This variety has medium heading date of Aug. 13, medium culm length of 78 cm and tolerance to lodging. It has also relatively semi-erect pubescent leaf blades and slightly tough culm with good canopy architecture. Gopumbyeo has a bit less number of tillers per hill and more spikelets per panicle than Hwaseongbyeo. It shows less sensitivity to premature heading in delayed transplanting of 50-day old seedlings. It showed longer delay of heading date but higher spikelet fertility than Hwaseongbyeo when exposed to cold stress. This variety shows delayed leaf senescence and considerable tolerance to viviparous germination during ripening. It shows moderate resistance to leaf blast, and bacterial blight, but susceptibility to stripe virus and insect pests. The milled rice of Gopumbyeo exhibits translucent, clear non-glutinous endosperm and medium short grains. It shows similar amylose content of 19.6%, and gelatinization temperature, and better palatability of cooked rice compared to Hwaseongbyeo. The milled rice yield of this variety is about 5.48 MT/ha at ordinary culture in local adaptability test for three years. Gopumbyeo would be highly adaptable to the central lowland and mid-southern mountainous areas of Korea.

An efficient system of rice microspore culture could contribute to the production of genetically modified rice. The microspores were isolated by mechanical or shed methods. The number of microspores per 100 anthers isolated at uninucleate stage was higher than (or similar to) those at binucleate stage in isolation method with pestle or spatular, but microspore divisions were not easily observed on both stages. On the other hand, pollen division in shed pollen culture was observed more frequently at uninuclear than at binuclear stage. Cold pretreatment at 10~circC for 10 days resulted in the best multicellular division to produce microcalli at 12.5% efficiency in shed microspores. Heat shock at 33~circC for one hour before or after pollen shedding enhanced cell division and callus formation. Out of twelve green regenerants, two were haploids and ten were diploids based on the chromosome analysis of root tips. The size of stoma was 12m m in haploids and 15 ~mu~textrmm in diploids determined by scanning electron microscope (SEM).