对Yr5致病的小麦条锈菌新菌系的毒性生物学特征、毒性变异与潜在流行风险

小麦条锈病由条形柄锈菌小麦专化型引起的，是我国小麦生产上最具毁灭性的生物灾害，严重威胁小麦安全生产。新菌系的出现和累积引起小麦“丧失”条锈病抗性，往往发展成流行小种，引起条锈病流行造成大幅减产。毒性变异是新小种产生的根本原因，对条锈菌群体演化起着重要作用。Yr5是对条锈病长期保持抗性的基因并被用于主栽品种的抗条锈病育种。申请人近期监测到对Yr5致病的新菌系，不同于当前优势流行小种CYR34和CYR32，毒性更强。该新菌系能否发展成流行小种，毒性演化规律与进化趋势直接对我国小麦生产安全构成巨大潜在威胁。本项目拟通过对新菌系的毒性、消长动态、寄生适合度、对主栽品种的致病性进行测定，综合分析新小种的潜在流行风险；利用基因组学方法解析该新菌系有性生殖后代与自然进化群体的毒性变异机理和毒性进化趋势。针对性地指导合理利用抗病品种可持续防控条锈病和预见性指导地小麦抗条锈病育种，保障我国小麦生产安全。

Wheat stripe rust (or yellow rust), caused by Puccinia striiformis Westend. f. sp. tritici Eriks. (Pst), is most destructive biological disaster, seriously threatening safe production of wheat in China. new isolates of the rust pathogen appeared and developed to predominant races that resulted in the loss of the resistance of wheat cultivars and caused large-scale pandemics of wheat stripe rust as well as tremendous yield reduction of wheat. Virulence variation is essential for generation of new races and plays an important role in virulence evolution of Pst population. Yr5，a long-term effective resistance gene to wheat stripe rust, is being used in breeding main cultivated wheat cultivars to stripe rust. More recently, the applicant detected a new Pst isolate virulent to the Yr5 gene, distinguishing from the current predominant Pst races CYR34 and CYR32 and representing more virulent than the two races. The facts whether the new Pst isolate can develop to epidemically predominant race and how about the trend and mechanism of virulence evolution, potentially threatening safe production of wheat in China. This study is to aim at comprehensive evaluation of potential epidemic risk based on tests on virulence / avirulence, population dynamics, parasitic fitness, pathogenicity to major cultivated wheat cultivars of the new isolate, and also at uncovering mechanism of virulence variation and the trend of virulence evolution of selfed progenies developed from sexual reproduction and the new isolate-derived isolates virulent to Yr5 using genomic approaches. The result will be used to guide to specifically utilize resistant wheat cultivars for sustainable control of wheat stripe rust and to predictably breed stripe rust-resistant wheat cultivars, protecting safe production of wheat in China.