Table1_Yellow Rust Epidemics Worldwide Were Caused by Pathogen Races from Divergent Genetic Lineages.doc

We investigated whether the recent worldwide epidemics of wheat yellow rust were driven by races of few clonal lineage(s) or populations of divergent races. Race phenotyping of 887 genetically diverse Puccinia striiformis isolates sampled in 35 countries during 2009–2015 revealed that these epidemics were often driven by races from few but highly divergent genetic lineages. PstS1 was predominant in North America; PstS2 in West Asia and North Africa; and both PstS1 and PstS2 in East Africa. PstS4 was prevalent in Northern Europe on triticale; PstS5 and PstS9 were prevalent in Central Asia; whereas PstS6 was prevalent in epidemics in East Africa. PstS7, PstS8 and PstS10 represented three genetic lineages prevalent in Europe. Races from other lineages were in low frequencies. Virulence to Yr9 and Yr27 was common in epidemics in Africa and Asia, while virulence to Yr17 and Yr32 were prevalent in Europe, corresponding to widely deployed resistance genes. The highest diversity was observed in South Asian populations, where frequent recombination has been reported, and no particular race was predominant in this area. The results are discussed in light of the role of invasions in shaping pathogen population across geographical regions. The results emphasized the lack of predictability of emergence of new races with high epidemic potential, which stresses the need for additional investments in population biology and surveillance activities of pathogens on global food crops, and assessments of disease vulnerability of host varieties prior to their deployment at larger scales.

本研究旨在探明近年全球小麦条锈病（wheat yellow rust）的暴发流行，究竟由少数克隆谱系的致病小种，还是由具有遗传分化的小种种群所驱动。本研究对2009至2015年间从35个国家采集的887株遗传多样性丰富的条形柄锈菌（Puccinia striiformis）分离株进行了小种表型分型，结果显示，这类流行病害通常由少数但遗传分化程度极高的谱系对应的小种主导。PstS1在北美地区占绝对优势；PstS2多见于西亚与北非；东非地区则同时存在PstS1与PstS2两种谱系。PstS4在北欧的小黑麦（triticale）种植区流行；PstS5与PstS9多见于中亚地区；而PstS6则在东非的病害流行中占据优势。PstS7、PstS8与PstS10则是欧洲地区流行的三大遗传谱系。其余谱系对应的小种则仅占较低的检出频率。对Yr9与Yr27（yellow rust resistance gene Yr9、Yr27）的毒力在非洲与亚洲的病害流行中较为常见，而对Yr17与Yr32的毒力则在欧洲地区占优，这与当地广泛推广种植的抗病品种所携带的抗病基因相吻合。南亚地区的菌株种群展现出最高的遗传多样性，此前已有研究报道该区域存在频繁的基因重组现象，且该区域未出现占绝对优势的特定小种。本研究结合病原菌入侵事件对全球各区域病原种群结构的塑造作用，对上述研究结果展开了讨论。研究结果凸显了具备高流行潜力的新型致病小种的出现难以预测，这也提示我们亟需加大针对全球粮食作物病原菌的种群生物学研究与监测工作，以及在大规模推广种植寄主品种前开展其病害易感性评估的投入力度。