13 ERA-CAPS BARLEY NAM - Locating exotic genes that control agronomic traits under stress in a wild barley nested association mapping (NAM) population

面对气候变化，要实现可持续的粮食生产，减少化肥和农药的投入，就需要在作物改良方面进行一场革命。与此同时，现代农作物的基因多样性正日益枯竭。扩展作物生物多样性和支持未来的作物改良可以通过“挖掘”祖先野生种质基因的等位基因变体来实现。利用多亲本育种群体和应用基因组学革命的新策略为利用外来种质进行育种提供了一条有前途的途径。我们将测试这两种方法使用野生大麦（大麦ssp。spontaneum）作为模式来改善栽培大麦在非生物和生物胁迫条件下的农艺表现。为此，我们将探索一种巢式关联作图（NAM）方法，使用第一个谷物NAM群体HEB-25（“哈雷外来大麦”）同时测试25个野生大麦种质的有益基因效应。HEB-25由1，420个BC 1 S3株系组成，每个株系携带约100个BC 1 S3基因。25%的野生大麦基因组来自25个外来供体之一，受体春大麦品种Barke的遗传背景为75%。首先，将评估HEB-25系的等位基因含量，采用最先进的外显子组捕获与下一代测序（EC-Seq）来发现1，420个HEB-25系中的每一个中的21，643个基因的单核苷酸多态性（SNP）。我们预计将绘制大约400，000个SNP，每个基因给出几个SNP，目的是区分任何野生大麦等位基因与受体Barke等位基因。其次，HEB-25品系将在德国、苏格兰和以色列的田间试验中栽培，以评估在氮缺乏、干旱或病原体攻击下的表型胁迫表现。将对形态、农艺和营养含量性状以及对重要大麦疾病叶锈病、黄锈病和网斑病的抗性进行评分。此外，将在以色列利用最新遥感技术对农艺表现进行建模，以建立非侵入性表型预测模型。第三，收集的数据集将在哈雷的中央数据仓库中存档并进一步处理，该数据仓库围绕一个定制的网络访问关系数据库建立，从而使项目输出的普遍访问成为可能。第四，由此产生的基因型和表型数据集将在全基因组关联扫描（GWAS）中结合起来，以确定野生大麦等位基因，这些等位基因可以改善植物在胁迫下的表现。由于基因分辨率极高，本研究将产生个体高置信度的候选等位基因，这些候选等位基因可直接调节所研究的性状。第五，为了在后续研究中验证所鉴定的性状改良外来等位基因，将在哈雷通过回交培育来自最初研究的HEB-25系的高分辨率后代群体。一方面，将使用开发的回交系详细研究新HEB性质的分子调控。另一方面，性状改良的外来等位基因将用于未来的育种计划。这将最终导致新的优良大麦品种具有改善的性能，同时，扩大我们的现代优良大麦基因库的生物多样性，由于纳入野生大麦种质。

Delivering sustainable food production in the face of climate change with reduced fertilizer and pesticide input requires a revolution in crop improvement. Meanwhile, modern crops are becoming increasingly depleted in gene biodiversity. Extending crop biodiversity and supporting future crop improvements can be achieved by 'mining' allelic variants of genes from ancestral wild germplasm. Novel strategies to utilize multi-parental breeding populations and apply the genomics revolution offer a promising route towards exploitation of exotic germplasm for breeding. We will test both approaches using wild barley (Hordeum vulgare ssp. spontaneum) as a model to improve agronomic performance of cultivated barley under abiotic and biotic stress conditions. For this, we will explore a nested association mapping (NAM) approach using the first cereal NAM population HEB-25 ('Halle Exotic Barley') to simultaneously test 25 wild barley accessions for beneficial gene effects. HEB-25 consists of 1,420 BC1S3 lines, each of which carrying ca. 25% of wild barley genome from one of 25 exotic donors on a 75% genetic background of the recipient spring barley cultivar Barke. First, the HEB-25 lines will be assessed for allele content, employing state-of-the-art Exome Capture with Next Generation Sequencing (EC-Seq) to discover single nucleotide polymorphisms (SNP) for 21,643 genes in each of the 1,420 HEB-25 lines. We expect to map roughly 400,000 SNPs, giving several SNPs per gene with the goal to distinguish any wild barley allele from the recipient Barke allele. Second, the HEB-25 lines will be cultivated in field trials in Germany, Scotland and Israel, to assess phenotypic stress performance under either nitrogen deficiency, drought or pathogen attack. Morphologic, agronomic, and nutrient content traits will be scored, as well as resistances against the important barley diseases leaf rust, yellow rust and net blotch. In addition, agronomic performance will be modeled in Israel by up-to-date remote sensing technology, to establish non-invasive phenotype prediction models. Third, the collected data sets will be archived and further processed in a central data warehouse at Halle, built around a custom web-accessible relational database, enabling universal access to the project outputs.Fourth, the resulting genotypic and phenotypic data sets will be combined in a Genome-Wide Association Scan (GWAS) to identify wild barley alleles that improve plant performance under stress. Because the gene resolution is extremely high this study will yield individual high confidence candidate alleles that putatively regulate the studied traits.Fifth, to validate the identified trait-improving exotic alleles in follow up studies, high-resolution offspring populations derived from the originally studied HEB-25 lines will be developed in Halle by backcrossing.The expected outcome of the BARLEY-NAM project will be beneficial in two directions. On one hand, the molecular regulation of new HEB properties will be studied in detail using the developed backcross lines. On the other hand, trait improving exotic alleles will be used in future breeding programs. This will ultimately lead to new elite barley cultivars with improved properties and, simultaneously, extend the biodiversity of our modern elite barley gene pool due to the incorporation of wild barley germplasm.