Characterisation of major genes (Stb)-mediated resistance to Septoria tritici blotch disease in wheat

小麦主基因（Stb）介导的小麦斑枯病抗性的表征

• 批准号: 2118081
• 金额: --
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2118081
• 关键词: Characterisation; major; genes; Stb; mediated

Wheat is one of the most important staple food crops providing 20% of total daily calories consumed by humans worldwide. Septoria tritici blotch (STB) is a devastating disease encountered in most wheat growing areas of the world and is the primary foliar disease of wheat in the UK responsible for year-on-year wheat losses of 5-10% despite fungicide treatments. The causal agent of STB is the fungus Zymoseptoria tritici. Emergence and spread of fungicide resistance in fungal populations seriously threatens wheat production and compromises food security, therefore resistance to STB is an important target in wheat breeding. To date, 21 major (Stb) genes and several quantitative trait loci (QTL) that make smaller contributions to the resistance phenotype have been identified and mapped genetically. Only one of these genes has so far been cloned and mechanisms of resistance remain poorly understood. Owing to a lack of well-defined QTLs with additive effects and near absence of diagnostic markers, the current STB resistance breeding strategies rely mostly on phenotypic evaluation of breeding materials rather than targeted genotyping based selection. Consequently, over the past decades, there has been only a modest improvement of STB resistance in the commercial wheat germplasm and the majority of current AHDB recommended UK wheat cultivars show only moderate resistance to STB.Published genetic maps at Stb loci are mostly low resolution and often involve early generation markers (eg RFLP, SSR), which are considered impractical in modern marker-assisted breeding. It is not known whether any of the Stb genes (apart from Stb6) may be present in the UK commercial wheat, or how effective these may be in controlling STB under UK conditions. The proposed PhD project, aims to fill this significant void in wheat breeding research by enhancing our understanding of genetics and mechanisms of STB resistance controlled by known Stb genes through addressing the following objectives:1.Identify frequency of virulence/avirulence in the current UK field Z. tritici populations towards each Stb gene, and whether any of these genes confer broad-spectrum resistance2.Assess whether resistance operates at seedling and/or adult plant stage3.Fine-map the most interesting and useful resistance gene(s), and develop the diagnostic second generation genetic markers (KASP) for use in breeding4.Gain insight into how the Stb gene(s) are conferring resistanceThe Stb genes will be transferred by crossing from foreign and exotic genotypes into a highly susceptible UK wheat background. Development of mapping populations nearly-isogenic lines is already in progress. These materials will then be phenotyped with current UK field Z. tritici isolates under glasshouse conditions followed by high-density genotyping. We have recently cloned Stb6 and shown that it encodes a Wall-associated receptor-like kinase (WAK) protein that defines a novel class of disease resistance proteins (Nat Genet, accepted). Using the latest IWGSC assembly of wheat genome, we have annotated and manually curated all WAK encoding genes and hypothesised that at least some of these may correspond to Stb genes. Indeed, bioinformatics analyses have indicated that several Stb loci correspond to physical intervals containing one or more WAK genes. The student will further test the above hypothesis by assessing the function of candidate WAK genes using Virus-induced gene silencing (VIGS) approach well established in our laboratory (Plant Physiol 160: 582-90). Mechanisms resistance conferred by the Stb genes will be investigated using a combination of molecular biology and bioimaging approaches, in particular determining whether disease resistance is associated or not with cell death, what step in the fungal lifecycle is being targeted, and what defence pathways are activated. The knowledge gained will aid breeding for STB resistance and therefore help to enhance crop productivity.

小麦是最重要的主粮作物之一，提供全世界人类每日消耗总热量的 20%。小麦斑枯病 (STB) 是世界上大多数小麦种植区遇到的一种毁灭性病害，也是英国小麦的主要叶部病害，尽管经过了杀菌剂处理，仍导致小麦同比损失 5-10%。 STB 的病原体是真菌小麦发酵壳孢 (Zymoseptoria tritici)。真菌群体中杀菌剂抗性的出现和蔓延严重威胁小麦生产和粮食安全，因此抗STB是小麦育种的重要目标。迄今为止，已鉴定出 21 个主要 (Stb) 基因和几个对抗性表型贡献较小的数量性状基因座 (QTL)，并进行了遗传图谱绘制。迄今为止，仅克隆了其中一个基因，并且人们对耐药机制仍知之甚少。由于缺乏明确的具有加性效应的 QTL 以及几乎缺乏诊断标记，目前的 STB 抗性育种策略主要依赖于育种材料的表型评估，而不是基于有针对性的基因分型的选择。因此，在过去的几十年里，商业小麦种质中的STB抗性仅略有改善，并且目前AHDB推荐的大多数英国小麦品种仅表现出对STB的中等抗性。已发表的Stb位点遗传图谱大多分辨率较低，并且通常涉及早期代标记（例如RFLP、SSR），这在现代标记辅助育种中被认为是不切实际的。目前尚不清楚英国商业小麦中是否存在任何 Stb 基因（Stb6 除外），也不知道这些基因在英国条件下控制 STB 的效果如何。拟议的博士项目旨在通过解决以下目标，增强我们对已知 Stb 基因控制的 STB 抗性的遗传学和机制的理解，从而填补小麦育种研究中的这一重大空白：1.确定当前英国田间小麦群体对每个 Stb 基因的毒力/无毒力频率，以及这些基因中的任何一个是否赋予广谱抗性2.评估抗性是否在幼苗和/或成年体中起作用 植物阶段 3. 精细绘制最有趣和最有用的抗性基因，并开发用于育种的诊断性第二代遗传标记 (KASP) 4. 深入了解 Stb 基因如何赋予抗性 Stb 基因将通过从外来和外来基因型杂交到高度易感的英国小麦背景中进行转移。群体近等基因系图谱的开发已经在进行中。然后，这些材料将在温室条件下用当前英国田间小麦分离株进行表型分析，然后进行高密度基因分型。我们最近克隆了 Stb6，并证明它编码一种 Wall 相关受体样激酶 (WAK) 蛋白，该蛋白定义了一类新型抗病蛋白（Nat Genet，已接受）。使用最新的小麦基因组 IWGSC 组装，我们注释并手动整理了所有 WAK 编码基因，并假设其中至少有一些可能对应于 Stb 基因。事实上，生物信息学分析表明，几个 Stb 基因座对应于包含一个或多个 WAK 基因的物理间隔。学生将通过使用我们实验室成熟的病毒诱导基因沉默 (VIGS) 方法评估候选 WAK 基因的功能来进一步测试上述假设 (Plant Physiol 160: 582-90)。将结合分子生物学和生物成像方法来研究 Stb 基因赋予的抗性机制，特别是确定抗病性是否与细胞死亡相关、真菌生命周期中的哪个步骤被针对，以及哪些防御途径被激活。获得的知识将有助于育种抗STB，从而有助于提高作物生产力。

项目成果

A large bioassay identifies Stb resistance genes that provide broad resistance against Septoria tritici blotch disease in the UK.

• DOI: 10.3389/fpls.2022.1070986
• 发表时间: 2022
• 期刊: FRONTIERS IN PLANT SCIENCE
• 影响因子: 5.6
• 作者: Tidd, Henry;Rudd, Jason J. J.;Ray, Rumiana V. V.;Bryant, Ruth;Kanyuka, Kostya
• 通讯作者: Kanyuka, Kostya