Yellowhammer: A multi-locus strategy for durable yellow rust resistance in wheat, in the face of a rapidly changing pathogen landscape

小麦是英国的主要粮食作物。小麦生产的一个主要制约因素是由条锈菌引起的小麦黄锈病。在未经处理的作物中，产量损失高达50%。抗病品种的使用和杀菌剂的使用是防治该病的两大主要措施。杀菌剂的应用是有效的，但成本高昂，受天气条件的限制，而且由于环境问题，使用越来越受到限制。寄主(即小麦)的抗性也非常有效，有几个已知的抗性基因对已知的PST小种具有免疫力。然而，当病原体发生突变时，病原菌的种群会定期变化，抗性基因突然变得无效。在欧洲，最近出现了一种外来的PST种群的快速入侵，这比它所取代的现有种群要多样化得多。因此，商业小麦品种的YR抗性模式发生了戏剧性的和持续的变化。仅在2016年，英国小麦推荐名单上的七个品种的抗性评级就大幅下降，对种植者造成了重大的成本影响。培育对当前和未来的入侵具有有效、持久的YR抗性的小麦改良品种是北欧(NE)小麦育种者的当务之急。在Yellowhmer，我们将采用基于检测和利用多个小种非特异成株抗性(APR)基因的策略，对该病进行长期遗传控制。这些基因通常提供部分抗性，其特征是病原菌生长减少和缓慢，并且可以相互‘堆叠’或与同一植物中的‘主要’基因一起提供有效的长期抗性。我们之前发现了几个APR基因，但寻找最有效的组合是具有挑战性的，因为不同的基因以复杂的方式相互作用。为了应对这一挑战，我们正在与七家东北育种公司和英国农业和园艺发展局合作，以欧洲精英品种为基础开发实验小麦种群，但它们携带的YR APR基因组合不同。我们将利用这些来：1.在东北地区12个地点进行为期四年的田间试验，确定最有效的APR基因组合，以及它们在季节中生效的时间。我们将研究什么是强和弱APR基因的最有效组合，以实现小麦对YR的抗性。我们还将确定APR基因在杂交小麦中的有效性以及APR基因对籽粒产量的任何副作用。利用微表型技术，确定参与病原菌-寄主相互作用的不同APR基因在植物中作用的时间和位置，帮助我们选择功能互补的APR基因进行组合。在不同的APR基因组合存在的情况下，确定哪些小麦基因和遗传途径被打开或关闭，以了解如何最好地组装具有互补分子遗传机制的APR基因组合。我们还将对新获得的群体和品种进行田间病理学试验，以确定新的APR基因。结果将使我们能够确定最佳的抗病等位基因组合，并提供新的遗传标记来辅助这一过程。结果将在活跃的商业育种材料中得到验证，并将立即转化为我们的商业合作伙伴的育种计划，使他们能够培育出更耐用的小麦品种，以抵御当前的PST种群和未来可能的入侵。这将改善英国的耕地产量和粮食安全，并减少对环境的危害，因为农民可以从获得表现更稳定、更持久、杀菌剂要求更少的品种中受益。

Wheat is the UK's major food crop. A major constraint on wheat production is the disease yellow rust (YR), caused by the fungus Puccinia striiformis f.sp. tritici (Pst), with yield losses up to 50% in untreated crops. The two major control measures for this disease, used in combination, are use of resistant varieties and application of fungicides. Fungicide application is effective but expensive, limited by weather conditions and increasingly restricted in use due to environmental concerns. Host (i.e. wheat) resistance can also be very effective, with several known resistance genes conferring immunity to known races of Pst. However, populations of the pathogen regularly change and resistance genes suddenly become ineffective when the pathogen mutates.In Europe, there was a recent rapid incursion of an exotic Pst population, which is much more diverse than the established population it has displaced. As a result, there have been dramatic and ongoing changes in the patterns of YR resistance in commercial wheat varieties. In 2016 alone, seven varieties on the UK wheat Recommended List had their resistance ratings substantially reduced, with significant cost impact on growers. Breeding improved wheat varieties with effective, long-lasting YR resistance to withstand current and future incursions is now a top priority for northern European (NE) wheat breeders.In Yellowhammer, we will employ a strategy based on detecting and utilizing multiple race non-specific adult plant resistance (APR) genes, for long-term genetic control of the disease. These genes usually confer partial resistance, are characterized by reduced and slower pathogen growth, and can be 'stacked' with each other or with 'major" genes in the same plant to provide effective long-lasting resistance. We previously identified several APR genes - but finding the most effective combinations is challenging as different genes interact with each other in complex ways. To address this challenge, we are collaborating with seven NE breeding companies and the UK's Agriculture and Horticulture Development Board to develop experimental wheat populations based on elite European varieties, but which differ in the combinations of YR APR genes they carry. We will use these to:1. Identify the most effective combinations of APR genes, and the times of the season they become effective, in field tests at twelve sites in NE over four years. We will investigate what is the most effective combination of strong and weak APR genes to achieve YR resistance in wheat. We will also determine the effectiveness of APR genes in hybrid wheat and any side-effects APR genes have on grain yield.2. Determine, using 'microphenotyping', the timing and location of action in the plant of different APR genes involved in the pathogen-host interaction, helping us select functionally complementary APR genes to combine.3. Identify which wheat genes and genetic pathways are switched on or off in response to the pathogen in the presence of different APR gene combinations in order to understand how to best assemble APR gene combinations with complementary molecular genetic mechanisms of resistance.We will also conduct field pathology trials of newly available populations and varieties to identify new APR genes.The results will allow us to determine the best combinations of resistance alleles to stack, and provide new genetic markers to aid the process. Results will be validated in active commercial breeding material and will immediately be translatable into the breeding programs of our commercial partners, enabling them to breed more durably resistant wheat varieties equipped to resist the current Pst population and potential future incursions. This will improve UK arable production and food security, and reduce environmental harm, as farmers benefit from having access to more consistently performing, longer-lasting varieties with reduced fungicide requirements.