Identification of quantitative trait loci associated with nitrogen use efficiency in winter wheat

Maintaining winter wheat (Triticum aestivum L.) productivity with more efficient nitrogen (N) management will enable growers to increase profitability and reduce the negative environmental impacts associated with nitrogen loss. Wheat breeders would therefore benefit greatly from the identification and application of genetic markers associated with nitrogen use efficiency (NUE). To investigate the genetics underlying N response, two bi-parental mapping populations were developed and grown in four site-seasons under low and high N rates. The populations were derived from a cross between previously identified high NUE parents (VA05W-151 and VA09W-52) and a shared common low NUE parent, ‘Yorktown.’ The Yorktown × VA05W-151 population was comprised of 136 recombinant inbred lines while the Yorktown × VA09W-52 population was comprised of 138 doubled haploids. Phenotypic data was collected on parental lines and their progeny for 11 N-related traits and genotypes were sequenced using a genotyping-by-sequencing platform to detect more than 3,100 high quality single nucleotide polymorphisms in each population. A total of 130 quantitative trait loci (QTL) were detected on 20 chromosomes, six of which were associated with NUE and N-related traits in multiple testing environments. Two of the six QTL for NUE were associated with known photoperiod (Ppd-D1 on chromosome 2D) and disease resistance (FHB-4A) genes, two were reported in previous investigations, and one QTL, QNue.151-1D, was novel. The NUE QTL on 1D, 6A, 7A, and 7D had LOD scores ranging from 2.63 to 8.33 and explained up to 18.1% of the phenotypic variation. The QTL identified in this study have potential for marker-assisted breeding for NUE traits in soft red winter wheat.

通过更高效的氮（N）管理维持冬小麦（普通小麦*Triticum aestivum* L.）的生产能力，可帮助种植者提升种植收益，并降低氮素流失带来的负面环境影响。因此，鉴定并应用与氮利用效率（nitrogen use efficiency, NUE）相关的遗传标记，将对小麦育种者产生极大助益。为解析小麦氮响应的遗传基础，本研究构建了两个双亲作图群体（bi-parental mapping populations），并在4个试验点季的低氮与高氮施肥水平下进行种植。两个群体均由前期已鉴定的高NUE亲本（VA05W-151与VA09W-52）与共享的低NUE亲本‘Yorktown’杂交选育而来：其中Yorktown × VA05W-151群体包含136个重组自交系（recombinant inbred lines），Yorktown × VA09W-52群体包含138个双单倍体（doubled haploids）。研究对亲本株系及其后代的11个氮相关性状开展表型数据采集，并通过测序分型（genotyping-by-sequencing）平台对基因型进行测序，在每个群体中检测到超过3100个高质量单核苷酸多态性（single nucleotide polymorphisms）。最终在20条染色体上共检测到130个数量性状位点（quantitative trait loci, QTL），其中6个在多个试验环境中与NUE及氮相关性状显著关联。上述6个与NUE相关的QTL中，2个分别对应已知的光周期基因（2D染色体上的*Ppd-D1*）与抗病基因（*FHB-4A*），2个为既往研究已报道的位点，另有1个QTL QNue.151-1D为新发现的位点。位于1D、6A、7A及7D染色体上的NUE相关QTL的LOD值范围为2.63至8.33，可解释最高达18.1%的表型变异。本研究鉴定的QTL具备应用于软红冬小麦NUE性状标记辅助育种（marker-assisted breeding）的潜力。