调控小麦种子休眠持续性主效QTL的精细定位

Preharvest sprouting (PHS) have serious effects on wheat yield and quality. It can be particularly severe if there is a long period of rainfall or a long period of high humidity after rainfall during harvest. Growing PHS-resistant cultivars with high level of seed dormancy and long dormancy duration is the most effective solution to minimize PHS damage. Whereas, QTL for seed dormancy level had been extensively reported, the QTL for seed dormancy duration had not been reported now. Previously, a total of 180 SSR markers were used to genotype 264 natural populations behaving distinct seed dormancy duration. The association analysis results showed that a stable QTL on chromosome 2AL (close to wmc658 marker) was detected to have major effects on seed dormancy duration across six environments in 2012 and 2013. In present study, multiple markers will be searched from reported articles previously and developed between extreme phenotype bulks derived from RILs population using SLAF-seq (specific-locus amplified fragment sequencing) technology. The polymorphic markers located in target interval will be further used to screen F7 RILs population. The selected residual heterozygous lines (RHLs) carrying heterozygous segments in target region are continuously selfed to produce secondary segregating F2 populations. Based on genotypic and phenotypic data, the major QTL was finely mapped in the target region. The SNP marker associated significantly seed dormancy duration will be identified and designed CAPS marker to assist wheat PHS resistance breeding. The fine mapping results will be further confirmed by using difference significance test.

小麦收获季节遭遇持续阴雨天气，会加剧穗上发芽，严重影响产量和品质。培育种子休眠水平高兼具休眠持续期长的品种有助于减轻持续阴雨天气造成的穗发芽危害。然而，目前种子休眠水平相关QTL报道较多，但种子休眠持续性相关QTL未见报道。申请人前期采用180对SSR标记，对种子休眠持续性差异显著的264份自然群体进行关联分析，结果在两年6种环境下鉴定一个与种子休眠持续性显著相关的主效QTL（2AL）。本研究拟以F7代RILs群体为基础，利用已报道的，以及采用简化基因组测序技术开发的SNP等多种标记，筛选该群体中目标位点附近杂合，而其他位点都纯合的剩余杂合单株，自交后构建RHL次级作图群体。通过分析其基因型，结合其种子休眠持续性表型数据，构建目标区段连锁图，精细定位主效QTL。采用RHL标记等位变异分组差异显著性分析进一步验证。筛选出显著相关的SNP等标记，开发CAPS等标记，用于抗穗发芽辅助育种。

小麦收获季节遭遇持续阴雨天气，会加剧穗上发芽，严重影响产量和品质。培育兼具种子休眠水平高且持续期长的品种是降低因持续阴雨天气所造成的穗发芽危害的一个有效途径。然而，目前有关种子休眠水平QTL报道较多，有关种子休眠持续性QTL及其候选基因报道较少。项目组利用关联分析在小麦2AL染色体上鉴定一个与种子休眠持续性显著相关的主效QTL，以携带该位点的济麦20/遂宁坨坨麦RILs群体以及201份微核心种质验证了该位点，通过筛选剩余杂合单株，构建次级分离群体，结合小麦90K和660K芯片在目标区域开发的CAPS标记，将主效QTL精细定位在0.31cM区间，并开发出与其紧密连锁的CAPS标记，用于抗穗发芽分子辅助育种。同时，本研究的精细定位区间信息可以为后续进一步克隆目标区域内的候选基因提供重要信息。