小麦乳熟期茎秆强度主效QTL的精细定位

Lodging is a key limiting factor to wheat production for high and stable yield. The milky stage is mostly prone to lodging. Improvement of stem quality and enhancing stem strength in wheat milky stage will reduce the risk of lodging. However, QTLs associated with stem strength in the milky stage were seldom studied. A new stable QTL(QSS.ahau-5A-2) for stem strength in milky stage on chromosome 5AL was detected by linkage mapping and association analysis, explaining 21.18% of phenotypic variation. In this project, the polymorphic markers located in the targeting interval will be further used to screen F6 RILs. The selected residual heterozygous lines (RHLs) carrying heterozygous segments in the targeting region are subsequently selfed to produce secondary segregating F2 populations. Based on genotypic and phenotypic data, the major QTL will be finely mapped in the targeting region, and it will be verified using the method of markers significant difference analysis of allelic variation packer of RHL-F2 population and RHL-F2:3phenotypic data. The SNP markers associated significantly with the QTL for stem strength will be identified. This study will enrich the understandings of genetic mechanism of wheat stem lodging tolerance, and also provide breeding resources and molecular markers for breeding varieties with lodging tolerance.

倒伏是小麦高产稳产的关键限制因素，小麦乳熟期极易发生倒伏；提高该时期茎秆强度，将有助于降低倒伏风险。目前，乳熟期茎秆强度QTL的研究还未见报道。申请人前期利用关联分析和连锁分析在5AL染色体定位一个小麦乳熟期茎秆强度主效QTL(QSS.ahau-5A-2)，可解释21.18%的表型变异，是一个新的位点。本研究拟以F6代RIL群体为基础，加密该区段，并利用多态性分子标记筛选该群体中仅在目标区域杂合的剩余杂合单株，构建RHL-F2次级作图群体。基于RHL-F2群体个体基因型和乳熟期茎秆强度表型数据，构建目标区段连锁图，精细定位该主效QTL。采用标记差异显著性测验方法分析RHL-F2群体不同等位变异间茎秆强度的差异，并用RHL-F2:3次级作图群体的乳熟期茎秆强度表型值进一步验证，筛选紧密连锁的SNP标记。本项目不仅丰富小麦抗倒伏遗传机理研究，而且为抗倒伏小麦新品种选育提供基因资源及分子标记。

倒伏是小麦高产稳产的限制因素，小麦乳熟期极易发生倒伏；提高该时期茎秆强度，将有助于降低倒伏风险。申请人前期通过126份自然群体的关联分析和安农0711/河农825 F2群体的连锁分析结果，在5AL染色体上定位一个小麦乳熟期茎秆强度主效QTL（Qssahau-5A-2）。本研究拟以安农0711/河农 825的RIL群体为基础，加密该区段，构建次级作图群体，精细定位该主效QTL，发掘紧密连锁的分子标记。在项目开展期间，基于SSR标记和茎秆强度高、低池660K芯片结果，将目标QTL（Qssahau-5A-2）定位在5AL染色体上gwm443-gwm156标记间，并开发了2个CAPS标记，其中AX-109445097位点开发的CAPS标记与Qssahau-5A-2连锁。基于660K芯片信息，检测了3B染色体上茎秆强度相关QTL，开发了13个CAPS标记；克隆了小麦第三同源群小麦木质素合成酶C4H基因序列，申请专利1项。前述5A、3B染色体上QTL定位不够精细，本研究进一步利用162个家系的55K芯片数据及6个生态环境下的茎秆强度表型值进行茎秆强度QTL定位，结果表明，前述定位到的5A、3B上茎秆强度QTL是易受环境影响的QTL；此外，在5D染色体上左、右置信区间3cM的区间内定位到一个与茎秆强度相关的稳定、主效QTL，分别可解释2018年淮北、2017年合肥、2017年阜阳的10.17%、9.88%、9.80%的茎秆强度表型变异，该结果利于后续茎秆强度精细定位工作的开展及标记开发。