Studies on the differentiation of genepools in rice

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Plant breeding is mainly to select favorable gene combinations from naturally occurring variants through hybridization. Since species have the primary genepool which is used as the genetic materials for their adaptation, the differential genepool is closely related with the difficulties in hybridization breeding. The objectives of the present study is to reveal the differentiated genepool among rice taxa and to examine the causal factors. The genic diversity was examined regarding to Wx and C genes controlling amylose content and anthocyanin coloration since these variations are distinct among cultivars than in wild relative regardless of the genetic bottleneck effects during the rice domestication. Sequence data of the Wx gene revealed that at least 5 alleles have been established after the domestication. The alleles resulted from frameshifts and changes in RNA processing and amino acids. The C gene showing allelic diversity in rice cultivars was found to be the homolog of maize cl encoding Myb-like protein.Sequence data showed that the frequency of non-synonymous mutations was high in the C of rice cultivars than the wild progenitor, indicating that such alteration in C might have been positively selected for during the domestication process. The internal barriers were also examined since they act as the mechanism of differentiated genepools. A hybrid sterility gene, S10, was located near wx and the candidate was detected by fine mapping and gene expression. In addition, at least 3 genes on chromosome 6 were found to play a significant role for cross-incompatibity in rice. The results will contribute for their molecular clonning to figure out their molecular evolution during the differentiation of genepools in rice.