Table2_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来全球小麦条锈病（wheat yellow rust）的流行是否由少数克隆谱系的生理小种，抑或是分化型小种种群所驱动。本研究对2009至2015年间采自35个国家的887份遗传多样性丰富的条形柄锈菌（Puccinia striiformis）分离物开展生理小种表型分型，结果显示此类病害流行通常由少数但遗传分化程度极高的谱系对应的小种所主导。PstS1谱系在北美地区占优势；PstS2谱系主要分布于西亚与北非；东非地区则同时存在PstS1与PstS2两种谱系。PstS4谱系在北欧的小黑麦（triticale）种植区流行；PstS5与PstS9谱系在中亚地区占据优势；而PstS6谱系则在东非的病害流行中广泛存在。PstS7、PstS8与PstS10则是欧洲地区流行的三大遗传谱系。其他谱系的小种则处于低频率分布状态。对条锈病抗性基因Yr9（resistance to yellow rust gene Yr9）与Yr27（resistance to yellow rust gene Yr27）的毒力在非洲及亚洲的病害流行中十分普遍，而对Yr17与Yr32的毒力则在欧洲广泛存在，这与当地大规模推广应用的抗条锈病基因相匹配。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谱系。本研究结合病原菌入侵在塑造不同地理区域病原种群结构中的作用，对上述研究结果展开讨论。本研究结果凸显了高流行潜力新小种出现的不可预测性，这也强调了需加大对全球粮食作物病原菌种群生物学研究与监测工作的投入，并在寄主品种大规模推广前开展病害风险评估的必要性。