Quantitative Trait Loci for Rice Heading Date in Koshihikari

To verify the quantitative trait loci (QTLs) for heading date in rice (Oryza sativa L.) variety Koshihikari, 3 mapping populations, i.e., 182 BC1F10 lines (backcross inbred lines, BILs) from Koshihikari/ Kasalath// Koshihikari, 40 chromosome segment substitution lines (CSSLs) from Kasalath/ Koshihikari, and 184 F10 lines (recombinant inbred lines, RILs) from Koshihikari/ Guichao 2, were planted in Nanjing, Jiangsu and Lingshui, Hainan in 2006. Three QTLs on chromosomes 3, 6, and 8 conferring heading date were detected in both environments using BILs. At qHd-3 and qHd-8 loci, the alleles from Koshihikari could shorten heading date for rice, whereas at qHd-6 locus, the allele from Koshihikari could delay heading date. Epistatic interaction was detected between qHd-3 and a QTL on chromosome 7. QTLs qHd-3 and qHd-7-1 were coincided with Kasalath segments of CSSLW008 and W020, respectively, and qHd-8 was coincided with CSSL W023 and W024 segments. In the Koshihikari/ Guichao 2 RIL population, three additive QTLs were detected on chromosomes 1, 7, and 11 in Nanjing environment and another 3 additive QTLs on chromosomes 6, 7, and 10 in Lingshui environment. Only 1 pair of epistatic QTLs with nonadditive effect was identified. These results provide a basis for breeding good quality rice cultivars with appropriate heading date.