Exploring effectors in Puccinia striiformis f. sp. tritici and identifying new sources of host resistance

作物病原菌危害全球粮食生产和条锈菌f.sp.小麦条锈菌(Tritici，PST)是引起小麦条锈病和黄锈病的主要病原菌之一，在加拿大和世界范围内危害最为严重。真菌孢子通过反复的侵染循环在小麦上无性繁殖，在有利的环境中可以引起疾病流行；这种多循环的疾病循环可以在一株感病的小麦植株上产生无数的夏孢子，一块作物田里的孢子数量是不可想象的。在这种情况下，即使是最低的随机突变率，加上宿主选择的压力，也会在种群中产生新的变种/小种。PST的生理小种或毒力表型是以携带已知的抗条锈病基因(yr基因)的小麦品种为特征的，通过我们过去的研究，我们已经在加拿大西部鉴定了35个PST小种。小麦-PST的致病系统遵循经典的基因对基因关系；为了成功地侵染小麦并克服YR基因的部署，PST使用一组武器，其中最重要的是‘效应器’或‘AVR基因’，然后由小麦的免疫受体感知这些基因来传递抗性。鉴定和鉴定PST效应子是我的研究计划的两个长期目标之一，它会导致小麦YR基因的毒力。我们对来自加拿大西部的PST种群的毒力表型和遗传谱系进行了广泛的表征(使用分子标记和全基因组测序)，并产生了大量的基因组资源。对于锈病治理来说，识别AVR效应子就是一半的战役，另一半的战役是加强小麦免疫系统。本研究的另一个主要目的是鉴定小麦及其近缘种对条锈病的抗性，进行遗传鉴定(作图、精细定位、克隆、功能鉴定)，并通过为小麦育种者创造预育种质来利用抗性。为此，我们已经鉴定了几个小麦抗病材料(栽培、野生和地方品种)，并从野生小麦中克隆了两个新的YR基因(未发表)。短期目标是利用现有的基因组资源，产生更多关于加拿大和来自其他国家的精选PST小种的基因组数据，以确定与我们克隆的YR基因相对应的AVR基因，并使用名为AgRenSeq的尖端基因克隆技术从野生小麦和Watkins地方品种中克隆新的YR基因。了解小麦的效应生物学和克隆新的YR基因将使我们能够为(加拿大和全球)农民培育更好的小麦品种抗性，因为该项目将提供关于PST所使用的‘武器’和病原体的进化潜力的知识。该项目将培训学生(在一个不同的实验室小组中)，让他们做好准备，成为自信的科学家，在学术界建立自己的研究项目，或者成为工业领袖。

Crop pathogens jeopardize global food production and Puccinia striiformis f. sp. tritici (Pst), the cause of stripe/yellow rust, is one of the most devastating wheat pathogens in Canada and worldwide. Fungal urediniospores are reproduced asexually on wheat via repeated cycles of infections and in conducive environments can cause disease epidemic; this polycyclic disease cycle can produce zillions of urediniospores on a single susceptible wheat plant and the number of spores in a single crop field can be unimaginable. In such scenarios, even the lowest rate of random mutation coupled with host selection pressure can give rise to new variants/races in the population. Physiologic races or virulence phenotypes of Pst are characterized on wheat genotypes carrying known stripe rust resistance genes (Yr genes) and through our past research we have characterized >35 Pst races in western Canada. The wheat-Pst pathosystem follows the classical gene-for-gene relationship; to successfully infect wheat and overcome deployed Yr genes, Pst uses a cocktail of weapons and the most important of those is 'effectors' or 'Avr genes' which are then perceived by immune receptors in wheat to confer resistance. Identification and characterization of Pst effectors, which results in virulence on wheat Yr genes, is one of the two long-term goals of my research program. We have extensively characterized Pst population from western Canada for virulence phenotypes and genetic lineages (using molecular markers and whole-genome sequencing) and have generated enormous genomic resources. For rust management, identification of Avr effectors is half the battle, the other half of the battle is to strengthen wheat immune system. Identification of stripe rust resistance in wheat & wheat relatives, genetic characterization (mapping, fine-mapping, cloning, functional characterization) and utilization of the resistance by generating pre-breeding germ plasm for wheat breeders is the other major goal of my research program. To this end, we have identified several accessions (cultivated, wild, and landraces) of wheat with resistance and have cloned two novel Yr genes (unpublished) from wild wheat panel. The short-term objectives are to utilize available genomic resources, generate more genomic data on Canadian and selected Pst races from other countries to identify Avr genes corresponding to our cloned Yr genes and clone novel Yr genes from wild wheat and Watkins landraces using cutting-edge gene cloning technology named AgRenSeq. Understanding effector biology and cloning of new Yr genes in wheat will enable us breed for better resistance in wheat varieties for farmers (in Canada and globally) because the project will deliver knowledge about the 'weapons' used by Pst and evolutionary potential of the pathogen. The project will train students (in a diverse lab group) to prepare them to become confident scientists & build their own research programs in academia or become leaders in industry.