2008 Volume 10 Issue 3 Pages 91-99
Grain appearance is one of the most important traits along with yield and palatability in rice production and breeding programs. To identify the chromosomal regions controlling grain appearance, we performed quantitative trait locus (QTL) analysis using chromosome segment substitution lines (CSSLs) derived from a cross between an indica cultivar, Kasalath (donor), and a japonica cultivar, Koshihikari (recurrent). The grain appearances of CSSLs were classified into six categories: perfect grains, immature white grains subclassified as white-back kernels, basal-white kernels, white berry kernels, milk-white kernels, and white core kernels. The ratios of kernels were used as traits in QTL identification. It was suggested that 12 chromosomal regions of chromosomes 1 (two regions), 2 (two regions), 5, 6, 7, 8, 9, 10, 11, and 12 were involved in QTLs for grain appearance. The total percentage of white-back and basal-white kernels was decreased by the substitution of the Kasalath chromosomal regions of chromosomes 2, 9, 11, and 12, but was increased by five regions of chromosomes 2, 5, 6, 8, and 10. The Kasalath alleles in one region of chromosome 1 and two regions of chromosomes 1 and 7 increased the proportion of white berry and milk-white kernels individually. Furthermore, we performed QTL mapping for grain appearance to validate the QTLs of chromosomes 1, 2, 5, and 12 using four F2 populations derived from a cross between CSSLs and Koshihikari. As a result, it was confirmed that four QTLs (RM3865 or RM3703 (chr2), RM1208 (chr12), S1946 (chr5), and RM8084 (chr12)) were involved in the gene causing phenotypic differences between the CSSLs and Koshihikari.
