Using novel genetic diversity for hybrid wheat pre-breeding

主题：农业与粮食安全过去四十年来小麦产量的稳步增长主要是由于育种者对优良近交系品种的遗传改良。然而，这一增长速度低于杂交作物，如玉米或甜菜。杂交种通常比同一作物的自交系品种产量更高。在理想条件下，立即改用杂交小麦估计可使产量增加3-15%，在次优条件下，其相对优势甚至更大。杂交品种被认为对环境压力的耐受性更强，并且可能在不同地点和年份表现出更高的产量稳定性。杂交品种也会给植物育种者带来更多的收入，从而增加育种活动，加快产量增长。杂种优势（杂种活力）发生在杂种优于其两个近交系亲本时，是杂合性的粗略功能。杂交育种通常使用“杂种池”：基于遗传相似性的种质分组。不同池间的杂交比同一池内的杂交杂合性更强。育种者努力识别或建立不同的杂种优势池，然后使它们进一步分离，增加杂合性，从而提高杂种优势水平。在BBSRC的小麦改良战略计划（WISP; BB/I002561/1）中，NIAB在冬季开发了数千个预育种品系(cv。六倍体小麦背景，基于再合成和宽杂交。KWS品种Robigus本身是一种野生小麦的衍生物，是许多英国精英品种的关键亲本成分。通过二倍体陶氏Aegilops tauschii （DD）与四倍体硬粒小麦（AABB）的杂交，重新合成引入了多样性。由此产生的再合成小麦（也称为SHW； AABBDD）可以常规用于与优质现代小麦品种杂交。在NIAB，通过四倍体和优良现代小麦品种之间的直接杂交，研究了A和b基因组的多样性。该项目将分为三个主要领域：1。评估育种前种质资源的遗传多样性，并根据NIAB的SHW和四倍体衍生的Robigus材料（“WISP系”）启动杂种优势池的开发。选择将交叉到KWS测试线生产F1混合动力车。同样的测试者也将与罗比古斯衍生的优良品种杂交。两组杂交品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品系的潜力。携带更多潜在籽粒位点的大穗是外来预育种材料（如WISP系）的共同特征。这种性状在高商业种植率时往往消失。然而，在杂交田中，播种率会较低，这可能导致大穗性状的更多表达。这一假设将通过在多个地点进行农艺试验来探讨，以比较在不同种植密度下生长的不同穗型的品系。杂种优势在抗病和最终使用品质等关键性状遗传控制中的重要性尚不清楚。RNAseq和其他转录组学方法将用于评估F1杂交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。这个育种前项目包括遗传学、转录组学、农学和标记辅助选择，并将在现代植物育种的各个方面提供彻底的基础。该项目将评估预育种材料在商业化F1杂交开发计划中的潜力。它将测试有关杂种优势池发育、农艺性状操纵和杂交基因表达的假设。该项目的受益者将包括：学术作物科学家。私营植物育种公司英国科学基地。更广泛的英国公众和政策制定者。科研人员包括经培训的候选人

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