水稻直播的普遍存在和低温冷害的频繁发生造成我国水稻每年大幅减产，培育芽期耐冷品种促使水稻快速立苗，是实现保产增产的前提条件。前期从地方籼稻湘743检测到一个芽期耐冷主效位点qSCT-8，效应38.94%。随后在新构建的重组自交系群体重复检测到qSCT-8，通过标记辅助选择（marker-assisted selection，MAS）从该群体筛选到包含目标位点杂合的2个剩余杂合体(residual heterozygous line, RHL)。本研究拟寻找并利用依次覆盖目标区间的多个剩余杂合体自交获得后代分离群体，从分离群体筛选自由组合和发生交换的不同近等基因系，通过比较区间与近等基因系表型分离的连锁关系对qSCT-8精细定位。通过杂交、回交并结合标记辅助选择将目的基因导入湘早籼45号，改良其耐冷性。研究结果为培育耐冷直播品种提供材料，为克隆基因、研究湘743耐冷遗传机制打下基础。

The popularization of directing seeding cultivation and frequency occurrence of low temperature cold damage caused significantly reduced yield of rice in china yearly. Improving cold tolerance at early seedling stage and promoting seedling to stand establishment uniformly is a prerequisite for realizing stable and increased yield in rice. In our previous study, a major QTL (qSCT-8) for cold tolerance at early seedling stage was identified with phenotypic variance of 38.94% from Hunan landrace rice Xiang743. Subsequently, the qSCT-8 was repeatedly detected in a newly constructed RIL population, two residual heterozygous lines (RHL) with heterozygous target regions were selected out from the RIL population using marker-assisted selection. In this paper, the RHLs with overlapping target intervals each other would be screened and used to produce some segregating populations, from which some isogenic lines (ILs) with different target regions would be selected out, fine mapping of qSCT-8 will be conducted using substitution mapping between multiple sets of ILs. Simultaneously the qSCT-8 will be transferred into Xiangzaoxian No.45 by crossing and backcrossing combined with MAS to improve cold tolerance of Xiangzaoxian No.45. The results lay a fundamental foundation for cloning gene and further elucidating genetic mechanism of cold tolerance in Xiang743.