基于单片段代换系的水稻苗期耐冷QTL的精细定位和聚合育种

Cold stress at the seedling stage is one of the key abiotic stresses in rice production in China. Developing cold-tolerant variety is the most economical and effective way to prevent cold damage. Cold tolerance at the seedling stage is an important character for stable rice production, especially in direct-seeded rice cultivation, which is becoming desirable in many Asian countries due to labor-use efficiency, low water use, and lower expense compared with transplanting seedling. Only with molecular breeding, the cold tolerance rice breeding can make a breakthrough at the seedling stage. Three SSSLs bearing stable cold tolerance QTL were identified using single segment substitution lines (SSSLs) which were developed by using of Hua-jing-xian74, an elite indica variety from South China, as recipient. The three cold tolerance QTLs were mapped on chromosomes 3, 6 and 12, respectively. So far, there aren’t reports of fine mapping for the three cold tolerance QTLs and cold tolerance molecular breeding at seedling stage. On the basis of precedent researches, this project aims to carry out the following researches:(1) Performing fine mapping of the three cold tolerance QTLs with substitution mapping; (2) Performing the pyramiding breeding for cold tolerance at seedling stage and making epistasis analysis of the three cold tolerant QTLs in rice. The completion of this project not only acquired the predicted genes of the three cold tolerance QTLs, but also gained some pyramiding lines with strong cold tolerance at seedling stage. The markers closely linked with the cold tolerance QTLs could be used for molecular breeding, and the pyramiding lines prove for the first time that pyramiding breeding could be utilized for cold tolerane at seedling stage in rice.

水稻苗期低温冷害是我国很多稻区的主要灾害之一。培育苗期耐冷品种不仅是目前水稻生产上急需解决的问题，更是适应农业现代化的需要。分子育种被认为是解决水稻苗期低温冷害的有效途径。但是，水稻苗期耐冷分子育种还未有成功的报道。准确鉴定效应较大并能稳定表达的耐冷QTL是水稻苗期耐冷分子育种取得突破的关键。本项目前期以优良品种“华粳籼74” 做轮回亲本构建的单片段代换系为材料，鉴定出3个苗期稳定表达的耐冷QTL，迄今未见这3个耐冷QTL被精细定位与克隆的报道。本项目拟在前期工作的基础上，将用代换作图法对3个耐冷QTL进行精细定位；并开展苗期耐冷QTL的聚合育种和3个耐冷QTL之间的互作效应分析。预期该项目的实施，不仅能预测这3个耐冷QTL的候选基因，获得的紧密连锁标记，可应用到分子育种中，而且首次实现苗期耐冷性聚合育种，获得的有显著苗期耐冷性优良聚合系有望应用于生产。

水稻苗期低温冷害是我国很多稻区的主要灾害之一。培育苗期耐冷品种是目前水稻生产上急需解决的问题。分子育种是解决水稻苗期低温冷害的有效途径。但是水稻苗期耐冷分子育种还未有成功的报道。.前期以优良品种“华粳籼74” （受体）构建的染色体片段代换系为材料，鉴定出3份苗期耐冷性稳定的代换系。在此基础上，通过高精度重测序及分子标记检测对代换系的代换区间进行了验证；并通过分离分析，找到了耐冷QTL的区间，构建了耐冷QTL的单片段代换系，表型鉴定显示有5个苗期耐冷QTL，分别位于第3（2个）、第6、第10和第12染色体上，这些QTL都能显著增加冷处理后的存活率；耐冷QTL qcts-3-1和qcts-3-2 的区间分别有3和2个基因注释到跟冷相关，分别是Os03g0785900, Os03g0786500, Os03g0801800 和Os03g0812400, Os03g0820700 ；耐冷QTL qcts-6 和qcts-12的区间分别有2个基因注释到跟冷相关，分别是Os06g 0107700, Os06g 0111800 ；Os12g 0610200, Os12g 0611200。耐冷QTL qcts-10 的区间有4个能导致氨基酸变化的基因。通过分子聚合育种，获得了双耐冷QTL（qCts-6/qCts-12）和三耐冷QTL（qCts-3-1//qCts-6/qCts-12）的聚合系，人工气候箱鉴定显示耐冷QTL qCts-6/qCts-12 以及qCts-3-1//qCts-6/qCts-12 的聚合都能显著提升苗期耐冷性。以存活率为指标，qCts-6 和qCts-12 之间不存在上位性效应（P=0.494）； 三个QTL qCts-3-1、 qCts-6、qCts-12 之间也不存在上位性效应（P=0.433）。三个耐冷QTL的累加比双QTL的聚合效应更好。在大田自然低温下的鉴定也证实，三耐冷QTL聚合系的苗期耐冷性得到了显著增强。.QTL的定位结果为下一步耐冷QTL的克隆以及高效的水稻苗期耐冷性分子育种的开展奠定了良好的基础；创制的耐冷QTL的聚合系，在人工气候箱和大田自然低温鉴定都证实显著提升了水稻苗期的耐冷性，将这些目标耐冷QTL导入到生产上的主推籼稻品种中，改良品种的苗期耐冷性，有望培育出在生产上应用的苗期耐冷品种，减少当前生产中水稻苗期冷害造成的损失。