Genetic effects of major QTLs controlling low-temperature germinability in different genetic backgrounds in rice (Oryza sativa L.).

The effects of QTLs are demonstrated basically within the population used in the original QTL analysis as the difference between the alleles of the parental varieties. For the efficient use of QTLs in breeding programs, it is necessary to assess whether the QTL exhibits its genetic effect when it is introgressed into different genetic backgrounds. Extensive studies of tolerance to low temperature at the seed germination stage (called low-temperature germinability) in rice revealed that 2 major QTLs on chromosomes 3 and 11, qLTG3-1 and qLTG11, have large effects. This study assessed the effects of these 2 QTLs from an aus variety, Kasalath, in different genetic backgrounds of 3 japonica varieties, Hoshinoyume, Hayamasari, and Koshihikari. Backcrossed progenies and chromosome segment substitution lines showed that both qLTG3-1 and qLTG11 were effective in the Hoshinoyume and Koshihikari backgrounds, while only qLTG3-1 was effective in the Hayamasari background. The results in this study demonstrated that these 2 QTLs are useful for the improvement of low-temperature germinability in rice breeding programs. The results also indicated that low-temperature germinability in rice is governed by an epistatic interaction of qLTG11.