To facilitate an active breeding strategy for rice quality improvement, mutation were induced by treating rice variety Sindongjin seeds with gamma ray(300 Gray) and its fertilized eggs with MNU(1mM). Endosperm and grain shape of mutants were classified and selected in M2 population. From M2 generation, 48(7.6%) endosperm mutants and 179(11.9%) grain shape mutants were selected. White belly and White core were the most frequent. Selected grain mutants were classified into 16 types according to their morphological phenotypes. The overall segregation ratio was 3 : 1, controlled by one gene. Specially, SM-17 and SM-20 displayed segregation ratio of 9 : 7 and 1 : 15 respectively. Grain mutants showed generally earlier heading dates, shorter culm length and ear length than the parent. Grain length, grain width, and 1,000 grain weight were also mostly shorter and lower than the parent. In SEM analysis, each mutant type showed unique starch particle size and starch accumulation pattern. The density of polygonal cells and small inner corpuscles depending on amylose content decreased as following order - Waxy>Dull>Parent >White core. In SDS-PAGE analysis, SM-22 of Opaque group and SM-34 of Giant embryo group showed high glutelin polypeptide concentration. SM-23 of Floury group, SM-26 of Shrunken group, and SM-31 of Sugary group showed low concentration of total protein with variations in bands over 55kDa.

The present study was carried out to assess the genetic diversity, population structure and linkage disequilibrium in Korea. In model-based population, Korean rice germplasm were classified into four subpopulaton designated as indica cultivated, japonica cultivated, indica weedy, and japonica weedy were identified. Pair-wise estimates of FST indicated a different degree of differentiation between the four model-based populations with values ranging from 0.073 (between japonica cultivated and japonica weedy) and 0.474 (between japonica weedy and indica weedy). The indica weedy population appeared to be highly differentiated as compared to other populations. The indica cultivated have the highest gene diversity (0.58), followed by japonica cultivated (0.50), japonica weedy (0.42) and indica weedy (0.35). The total number of specific alleles in indica weedy and japonica weedy populations was 39 alleles (23 markers) and 55 alleles (22 markers), respectively. An average of LD (r2) value of indica weedy and japonica weedy type was higher than two other populations, both in inter- and intra-chromosome, indicating the possible reproductive and geographical isolations of sub-populations in cultivated rice fields.