小麦抗穗发芽主效QTL Qphs.ahau-6B的精细定位

Pre-harvest sprouting (PHS) significantly decreases wheat grain yield and quality, causing huge devastation in wheat industry, reported worldwide. The genes mining and pyramiding for PHS tolerance is an effective solution to develop wheat varieties resistant to pre-harvest sprouting. In my previous studies, a new stable PHS QTL on chromosome 6BL (Qphs.ahau-6B) was detected by association analysis and linkage mapping, explaining 10.6-19.2% of phenotypic variances. A finer mapping will aid for rapid identification of candidate PHS genes. Thus, the objectives of this project are to: (i) finely map the major QTL in F2，F2:3 and F3:4 secondary segregating population constructed by two lines JW25 and JW105 (JW25 has an allele at Qphs.ahau-6B locus for higher PHS tolerance, whereas JW105 has an allele at Qphs.ahau-6B locus for lower PHS tolerance) using markers converted from SNPs of wheat 660K SNP array in RIL population, and those from BSR-Seq in F2 and F2:3 populations, and (ii) predict the candidate genes based on the closely linked SNP markers and IWGSC wheat reference genome sequence information. This study will improve the understandings of genetic mechanism of wheat PHS tolerance, and also provide resistance germplasm and molecular markers for breeding varieties with PHS tolerance.

小麦收获前穗发芽是一种世界性灾害，严重降低产量和加工品质；通过抗穗发芽基因的挖掘和聚合培育抗穗发芽小麦品种是解决问题的有效途径。项目申请人前期利用关联分析和连锁分析在小麦6BL染色体上定位到一个新的抗穗发芽主效QTL（Qphs.ahau-6B），可解释10.6-19.2%的表型变异。在此基础上，本项目拟利用660K芯片分析群体亲本和抗感池，筛选目标区段多态性SNP加密Qphs.ahau-6B区域；同时，参考目标QTL侧翼标记，用携带纯合抗穗发芽等位基因家系JW25和纯合感穗发芽等位基因家系JW105组合的次级群体F2、F2:3和F3:4为研究材料，通过对F2和F2:3两个世代的抗感池BSR-Seq分析，开发标记精细定位Qphs.ahau-6B，并参考小麦基因组序列信息预测候选基因，为抗穗发芽小麦新品种选育提供基因资源及分子标记。

小麦穗发芽是小麦在收获前遭遇连阴雨天气从而直接在麦穗上发芽的现象，它会导致小麦产量和品质的降低，给国家和农民带来巨大的经济损失。本课题组前期利用全基因组关联分析和QTL定位分析共同在小麦6BL染色体定位到一个与白皮小麦穗发芽抗性相关的新主效位点Qphs.ahau-6B，位于6B染色体上568.5Mb-575.6 Mb之间（峰值接近标记EX06323），区间长度为7.1 Mb。基于上述结果，本项目研究先以京411 × 万县白麦子 RIL群体为材料，结合660K芯片结果开发标记，结果将Qphs.ahau-6B精细定位于小麦6BL染色体上的标记W1-7与EX06323之间，物理位置为574.7 Mb-575.6 Mb，使得QTL区间长度从原来的7.1 Mb缩至0.9 Mb，能解释9.71％-22.90％的穗发芽表型变异。后以姊妹系JW27和JW120构建的F2:3群体和F3:4群体为试验材料，检测表型和基因型，对精细定位结果进一步验证。并对次级群体F2:3群体的抗感池进行BSR-Seq测序技术。结合BSR-Seq测序技术结果和Qphs.ahau-6B新定位区间在小麦参考基因组Chinese Spring genome v1.0中信息，推测TraesCS6B01G325500和TraesCS6B01G325900与胚休眠相关，可能是Qphs.ahau-6B的候选基因。该结果为白皮小麦抗穗发芽新品种选育提供基因资源及分子标记。