水稻芽期耐冷QTLqSCT-8的精细定位及MAS育种利用

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.

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。

水稻直播的大面积应用和低温冷害的频繁发生引起我国水稻每年大幅减产，挖掘芽期耐冷相关基因、培育耐冷品种是促使水稻在低温下快速立苗、实现保产增产的前提条件。本研究利用芽期耐冷地方稻资源湘743与冷敏感品种Katy杂交构建重组自交系群体，遗传分析并鉴定湘743芽期耐冷相关位点。在此基础上筛选目标位点区间杂合的剩余杂合体，发展次级群体对目标QTL进行精细定位。同时，利用芽期耐冷资源湘糯1号对湘早籼45号进行耐冷性改良。共鉴定了6个芽期耐冷相关QTL，分别分布在第1，2，3，8，10和12染色体上，均是来自于湘743等位基因增强芽期耐冷，共解释了36.8%的表型变异。其中位于第3染色体RM520-RM85区间的QTL qESCT-3 与先前检测到的qSCT-3位于相同的区间，且均是来自于湘743基因增强耐冷。为了精细定位QTL qESCT-3，从重组自交系群体中筛选目标区间杂合、其它背景基本纯合的两个剩余杂合体RHL948和RHL1058，发展了两个次级精细定位群体。在RHL948衍生群体中，qESCT-3被精细定位在RM520-RM227之间，LOD值为2.2，贡献率为6.98%。在RHL1058衍生群体中，qESCT-3被精细定位在RM520-RM227之间，LOD值为3.37，贡献率为10.93%。通过高通量RNA测序（RNA-Seq）结合目标区间表达分析，目前我们已经克隆了该基因，正在进行功能验证及耐冷分子机制分析。同时，以湘早籼45号为轮回亲本，芽期耐冷性极强的湘糯1号为供体，杂交后结合分子标记辅助连续回交，筛选到一个渗入系IL43，其田间农艺性状与湘早籼45号相似，但芽期耐冷性得到极大改良。本研究克隆的芽期耐冷基因为培育耐冷品种提供了基因资源，有助于水稻耐冷分子机制研究。同时，筛选的参入系为培育耐冷早稻品种提供了中间材料。