Genetic control of barb/trichome formation on barley awns and stigmata – or, why does cultivated barley need rough awns?

大麦芒是粗糙的，因为它们被高度硅化的倒钩覆盖。已知粗糙芒在谷物收获期间对人的呼吸道以及在以大麦为食时对一些反刍动物和其他动物的消化道造成危害。这一性状受几个主要的遗传位点控制，无刺芒或光滑芒的育种相对容易实现。然而，由于平滑芒与柱头多毛减少的相关性，这通常与大麦的育性降低有关，我们最近克隆了一个控制大麦芒糙度的主效基因Raw 1，并根据GWAS和双亲定位，在一个有希望的基因区域中确定了第二个位点，我们的目标是通过最先进的基于基因组学的定位克隆分离第二个位点，并对两个克隆的芒粗糙度基因进行基因功能分析。了解自然选择下的两个基因，并通过利用我在IPK的小组正在开发的泛基因组和遗传多样性资源，将有可能跟踪芒粗糙度性状的选择/驯化历史，并测试其与柱头多毛和生育力的联系/相关性，从而为未来的光滑芒表型育种提供知识，而不会通过降低生育力而造成产量损失。该项目旨在揭示大麦芒粗糙度的遗传基础及其与影响生育力和产量的柱头多毛的相关性。本研究的主要目的是：定位和克隆大麦染色体7 HS上新发现的光滑芒基因（Raw 7 HS）的功能基因;通过TILLING和定点突变验证新分离基因Raw 7 HS的功能;通过定点突变验证Raw 1控制芒粗糙度和柱头多毛的功能;揭示Raw 1和Raw 7 HS基因座的自然多样性和选择特征;·通过对来自自然多样性收集的粗糙、光滑和半光滑种质进行系统表型分析，测试倒钩形成和柱头多毛之间的功能联系;·对一组独立诱导的光滑/半光滑突变体进行表型和基因型（Raw 1和Raw 7 HS）表征，以揭示其等位基因状态。建立raw 1和raw 7 HS基因型与诱导突变体组之间的遗传杂交，以测试累积或上位相互作用，并建立作图群体，用于后续项目中的进一步基因分离。

Barley awns are rough because they are coated with highly silicified barbs. Rough awns are known to cause hazards for the human respiratory tract during grain harvest as well as for the digestive tract of some ruminants and other animals when foraging on barley. The trait is controlled by a few major genetic loci and breeding for barbless awns, or smooth awns, is relatively easy achievable. Because of a correlation of smooth awns with reduced stigma hairiness, which is often associated with reduced fertility in barley, however, rough awn remained the predominant form of cultivated barley.We have recently cloned a major gene Raw1 controlling awn roughness in barley and based on GWAS and bi-parental mapping we have delimited a second locus in a promising region for gene-cloning on barley chromosome 7HS.We aim to isolate the second locus by state-of-the-art genomics-based positional cloning and perform gene function analysis of both cloned awn roughness genes. Knowing both genes that were under natural selection and by exploiting the pan-genome and genetic diversity resources under development in my group at IPK, it will be possible to track the selection/domestication history of the trait awn roughness and test its linkage/correlation with stigma hairiness and fertility and thus provide the knowledge of future breeding for smooth awn phenotypes without yield penalty through reduced fertility. The project aims at revealing the genetic basis of awn roughness in barley as well as its correlation to stigma hairiness, which is influencing fertility and yield. The following objectives will be adressed:• Genetic mapping and cloning of the functional gene of the newly identified smooth awn locus on barley chromosome 7HS (Raw7HS);• Functional validation of the newly isolated gene Raw7HS by TILLING and site-directed mutagenesis;• Functional validation of Raw1 control of awn roughness and stigma hairiness through site-directed mutagenesis;• Reveal natural diversity and signatures of selection at the Raw1 and Raw7HS loci; • Test for functional linkage between barb formation and stigma hairiness through systematic phenotyping of rough, smooth and semi-smooth accessions from a natural diversity collection;• Phenotypic and genotypic (Raw1 and Raw7HS) characterisation of a panel of independently induced smooth / semi-smooth mutants to reveal their allelic state.• Establish genetic crosses between raw1 and raw7HS genotypes and the panel of induced mutants to test for cumulative or epistatic interactions and to establish mapping populations for further gene isolations in (a) subsequent project(s).