Using novel genetic diversity for hybrid wheat pre-breeding

布景主题：农业和粮食安全在过去的四十年里，小麦产量的稳步增长在很大程度上是由于育种者对优良自交系品种的遗传改良。然而，这一增长率低于玉米或甜菜等杂交作物。杂交品种通常比同种作物的近交品种更高产。在理想条件下，立即转向杂交小麦可能导致产量增加3-15%，在次优条件下甚至具有更大的相对优势。杂交种被认为对环境胁迫的耐受性更强，并且可能在不同地点和不同年份表现出更高的产量稳定性。杂种优势（杂种优势）是指一个杂交种的表现优于其两个自交亲本，这是杂合性的一个粗略函数。杂交育种通常使用“杂种优势库”：基于遗传相似性的种质分组。不同池之间的杂交将比同一池内的杂交更杂合。育种者努力工作，以确定或建立不同的杂种优势库，然后把他们进一步分开，增加杂合性，从而在随后的杂交种的杂种优势水平。在BBSRC的小麦改良战略计划（WISP; BB/I 002561/1），NIAB已经开发了数千个预育种系在一个冬天（cv. Robigus）六倍体小麦背景，基于再合成和远缘杂交。KWS品种Robigus本身是一种野生小麦衍生物，是许多英国精英品系的关键亲本成分。再合成通过将二倍体节节麦（DD）与四倍体硬粒小麦（AABB）杂交引入多样性。由此产生的再合成小麦（也称为SHW; AABBDD）可以常规地用于与优良的现代小麦品种杂交。NIAB也通过四倍体和优良现代小麦品种之间的直接杂交，对A和B基因组多样性进行了类似的探索。该项目将分为三大领域：1.评估育种前种质的遗传多样性，并启动基于NIAB的SHW和四倍体来源的Robigus材料（“WISP品系”）的杂种优势库的开发。选择将交叉到一个KWS测试线，以产生F1杂种。同一个测试者还将与Robigus衍生的优良品种杂交。这两组杂交种将在欧洲各地的试验中进行比较，以评估在杂交育种中使用WISP系的潜力。大穗携带更多潜在的谷粒位点是外来预育种材料如WISP系的共同特征。这种特性往往在高商业种植率下消失。然而，在杂交田中播种率将较低，这可能导致大穗性状的更大表达。这一假设将通过多个地点的农艺试验来探索，以比较在不同种植密度下生长的具有对比穗型的品系。杂种优势在抗病性和最终使用质量等关键性状的遗传控制中的重要性仍不清楚。RNAseq和其他转录组学方法将用于评估F1杂种相对于其近交亲本系在不同情况下生长的基因表达变化。该预育种项目包括遗传学，转录组学，农艺学和标记辅助选择，并将在现代植物育种的各个方面给予彻底的基础。该项目将评估前的潜力，育种材料在商业F1杂交发展计划。它将测试有关杂种优势库的发展，通过农艺性状的操纵和杂交种中的基因表达的假设。该项目的受益者将包括：1。学术作物科学家2.私营植物育种公司3.英国科学基地4.更广泛的英国公众和政策制定者5。研究科学家，包括通过培训的候选人

Theme: Agriculture and Food SecurityThe steady increase in wheat yields over the past forty years is largely due to genetic improvements in breeders' elite inbred varieties. However, this rate of increase is less than for hybrid crops such as maize or sugar beet. Hybrids are generally more productive than inbred varieties of the same crops. An immediate switch to hybrid wheat could lead to estimated yield increases of 3-15% under ideal conditions, with even greater relative advantages under sub-optimal situations. Hybrids are believed to be more tolerant of environmental stresses and may show increased yield stability across locations and years. Hybrids would also generate greater income for plant breeders, leading to increased breeding activity and acceleration in yield increase.Heterosis (hybrid vigour) occurs when a hybrid outperforms its two inbred parents, and is a crude function of heterozygosity. Hybrid breeding often uses 'heterotic pools': germplasm groupings based upon genetic similarities. Crosses between different pools will be more heterozygous than crosses within the same pool. Breeders work hard to identify or establish distinct heterotic pools, and then to drive them further apart, increasing heterozygosity and thus heterosis levels in subsequent hybrids.Within BBSRC's Wheat Improvement Strategic Programme (WISP; BB/I002561/1), NIAB has developed thousands of pre-breeding lines in a winter (cv. Robigus) hexaploid wheat background, based on resynthesis and wide crossing. The KWS variety Robigus, itself a wild wheat derivative, is a key parental component in many elite UK lines. Resynthesis introduces diversity through crossing diploid Aegilops tauschii (DD) with tetraploid durum wheat (AABB). The resulting resynthesised wheat (also called SHW; AABBDD) can be used routinely in crosses with elite modern wheat varieties. A- and B-genome diversity has similarly been explored at NIAB through direct crosses between tetraploids and elite modern wheat varieties. The project will be broken down into three broad areas:1. Assess genetic diversity in pre-breeding germplasm and initiate the development of a heterotic pool based on NIAB's SHW- and tetraploid-derived Robigus material ('WISP lines'). Selections will be crossed to a KWS tester line to produce F1 hybrids. The same tester will also be crossed with Robigus-derived elite varieties. Both sets of hybrids will be compared in trials across Europe to evaluate the potential of using WISP lines in hybrid breeding.2. Large ears carrying more potential grain sites are a common feature of exotic pre-breeding material eg WISP lines. This trait often disappears at high commercial planting rates. However, seeding rates will be lower in hybrid fields, which may lead to greater expression of the large ear trait. This hypothesis will be explored through agronomy trials at multiple locations to compare lines with contrasting ear types grown at different planting densities.3. The importance of heterosis in the genetic control of key traits such as disease resistance and end-use quality remains unclear. RNAseq and other transcriptomic approaches will be used to assess the changes in gene expression for F1 hybrids relative to their inbred parental lines, grown in different situations.This pre-breeding project encompasses genetics, transcriptomics, agronomy and marker-assisted selection, and will give a thorough grounding in all aspects of modern plant breeding.This project will evaluate the potential of pre-breeding material in a commercial F1 hybrid development programme. It will test hypotheses about heterotic pool development, the manipulation of traits through agronomy, and gene expression in hybrids. The beneficiaries of the project will include: 1. Academic crop scientists2. Private sector plant breeding companies3. UK science base4. The wider UK public and policy makers5. Research scientists, including the candidate via training