Identification of genetic factors controlling useful traits for Sake-brewing and development of evaluation methods on genetic resources of Sake-brewing rice

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1. Genetic analysis on white core and grain size was carried out using the following populations of rice.-F1 populations generated from diallel crosses between five cultivars for Sake-brewing and cooking rice.-Fl, F2 and backcross populations between Gohyakumangoku and Koshihikari.In addition, QTL analysis on white core and grain size was performed using recombinant inbred lines between Hyogokitanishiki and Nipponbare. As a result, major QTLs for these traits were detected on chromosomes 2 and 12.2. In order to identify the genes controlling useful traits for Sake-brewing, gene expression survey was carried out by SAGE method with ripening seeds of Yamadanishiki (Sake-brewing rice) and Reiho (cooking rice). One of the candidate genes showing strong variety-specific expression was Rsg1 which codes 13 kDa of prolamin. Based on the gene structural analysis, Reiho was found to keep intact Rsg1 gene, whereas Yamadanishiki has inactive one because of the insertion of transposon-like sequences. QTL analysis on seed protein content was also carried out using 91 double haploid lines between Yamadanishiki and Reiho, and one QTL for protein content of 13 kDa prolamin was detected on chromosome 12, suggesting this locus correspond to Rsg1 gene.3. Allelic diversity at 76 SSR loci among 188 cultivars of Sake-brewing and cooking rice was examined. Based on these data, principal component analysis, cluster analysis and group structural analysis (by Markov Chain Monte Carlo Method) were carried out. As a result, 188 cultivars were classified into 10 subgroups. Of these, three groups (named as Yamadanishiki, Gohyakumangoku and Hanafubuki groups) were found to consist of majority of Sake-brewing rice cultivars.