A doubled haploid population, derived from anther culture of F-1 hybrid between a typical indica cv. and a japonica cv. has been used to investigate the seedling cold tolerance (SCT) in growth cabinet, By dynamically analyzing every day's survival percentages of the parents and DH lines under 7-d cold plus 9-d normal temperature condition, the quantitative trait loci (QTLs) for SCT have been mapped based on a molecular linkage map constructed from this population. The results show that two parents had significant differences in SCT and the segregation of SCT in DH lines was basically a continuous distribution with most serious injury on the 6th d of the cold treatment. A total of 4 QTLs for SCT have been identified on chromosomes 1, 2, 3 and 4 respectively. The additive effects of qSCT-1, qSCT-2 and qSCT-3 have been contributed by the japonica cv JX17, but that of qSCT-4 has been contributed by the indica cv ZYQ8. The mechanism of SCT seems complicated since the above 4 QTLs detected at different stages during the treatment. Further study on the genotypes for these SCT QTLs in the DH lines shows transgressive segregation. It is demonstrated that the lines with stronger SCT over JX17 have 3-4 loci for SCT. Integration of these QTLs into an appropriate variety may lead to a successful rice breeding program for cold tolerance.
