QTLs Associated with Agronomic Traits in the Cutler × AC Barrie Spring Wheat Mapping Population Using Single Nucleotide Polymorphic Markers

We recently reported three earliness per se quantitative trait loci (QTL) associated with flowering and maturity in a recombinant inbred lines (RILs) population derived from a cross between the spring wheat (Triticum aestivum L.) cultivars ‘Cutler’ and ‘AC Barrie’ using 488 microsatellite and diversity arrays technology (DArT) markers. Here, we present QTLs associated with flowering time, maturity, plant height, and grain yield using high density single nucleotide polymorphic (SNP) markers in the same population. A mapping population of 158 RILs and the two parents were evaluated at five environments for flowering, maturity, plant height and grain yield under field conditions, at two greenhouse environments for flowering, and genotyped with a subset of 1809 SNPs out of the 90K SNP array and 2 functional markers (Ppd-D1 and Rht-D1). Using composite interval mapping on the combined phenotype data across all environments, we identified a total of 19 QTLs associated with flowering time in greenhouse (5), and field (6) conditions, maturity (5), grain yield (2) and plant height (1). We mapped these QTLs on 8 chromosomes and they individually explained between 6.3 and 37.8% of the phenotypic variation. Four of the 19 QTLs were associated with multiple traits, including a QTL on 2D associated with flowering, maturity and grain yield; two QTLs on 4A and 7A associated with flowering and maturity, and another QTL on 4D associated with maturity and plant height. However, only the QTLs on both 2D and 4D had major effects, and they mapped adjacent to well-known photoperiod response Ppd-D1 and height reducing Rht-D1 genes, respectively. The QTL on 2D reduced flowering and maturity time up to 5 days with a yield penalty of 436 kg ha-1, while the QTL on 4D reduced plant height by 13 cm, but increased maturity by 2 days. The high density SNPs allowed us to map eight moderate effect, two major effect, and nine minor effect QTLs that were not identified in our previous study using microsatellite and DArT markers. Results from this study provide additional information to wheat researchers developing early maturing and short stature spring wheat cultivars.

本团队此前曾利用488个微卫星（microsatellite）与多样性芯片技术（diversity arrays technology，DArT）标记，在春小麦（Triticum aestivum L.）品种‘Cutler’与‘AC Barrie’杂交构建的重组自交系（recombinant inbred lines，RILs）群体中，报道了3个与开花期和成熟期相关的固有早熟性数量性状位点（quantitative trait loci，QTL）。本研究基于同一群体，利用高密度单核苷酸多态性（single nucleotide polymorphic，SNP）标记，鉴定与开花期、成熟期、株高及籽粒产量相关的QTL。我们对由158个重组自交系及其2个亲本构成的作图群体，在5个大田环境下开展开花期、成熟期、株高与籽粒产量的表型鉴定，在2个温室环境下开展开花期表型鉴定；同时采用90K SNP芯片中的1809个SNP子集与2个功能标记（Ppd-D1与Rht-D1）进行基因分型。通过对多环境表型数据进行复合区间作图法分析，我们共鉴定得到19个与目标性状相关的QTL：其中温室条件下开花期相关QTL 5个、大田条件下开花期相关QTL 6个，成熟期相关QTL 5个、籽粒产量相关QTL 2个、株高相关QTL 1个。这些QTL分布于8条染色体上，单个QTL可解释6.3%至37.8%的表型变异。19个QTL中有4个同时与多个性状相关：包括2D染色体上与开花期、成熟期及籽粒产量相关的QTL；4A与7A染色体上与开花期、成熟期相关的2个QTL；以及4D染色体上与成熟期、株高相关的QTL。但仅2D与4D染色体上的QTL具有主效效应，二者分别紧邻已知的光周期响应基因Ppd-D1与降秆基因Rht-D1。2D染色体上的QTL可将开花期与成熟期缩短最多5天，但会带来436 kg·ha⁻¹的产量损失；而4D染色体上的QTL可使株高降低13 cm，但会使成熟期延长2天。高密度SNP标记帮助我们鉴定得到8个中等效应、2个主效效应与9个微效效应的QTL，这些位点均未在本团队此前利用微卫星与DArT标记的研究中被发现。本研究结果可为春小麦育种研究者培育早熟、矮秆春小麦品种提供额外的参考信息。