Goss's wilt and blight of maize, caused by Clavibacter nebraskensis, is an important disease in the USA and Canada. The re‐emergence of Goss's wilt in the mid‐2000s and the subsequent spread of this disease probably resulted from changes in crop management practices and possibly changes in the pathogen population. The objectives of this study were to determine the genetic diversity and phylogeny of strains of C. nebraskensis associated with recent and historic Goss's wilt epidemics in the north Central USA, to measure the effects of collection period on population structure, and to identify the phylogenetic status of avirulent strains of C. nebraskensis. Multilocus sequence analysis and typing were used to address these objectives. Bayesian analysis of the sequences of atpD, dnaK, and kdpA separated the type strain of C. nebraskensis from type or reference strains of three other Clavibacter spp. The 125 strains of C. nebraskensis used in this study formed a monophyletic taxon. Four lineages were identified. Clades I, II, and IV contained a high proportion of highly virulent strains from the Upper Midwest. Clade III contained a high proportion of strains from Nebraska, Colorado, and South Dakota collected between 1969 and 1998. A significant substructure was detected between subpopulations from historic outbreaks in Nebraska and Colorado and more recent outbreaks in Minnesota. Virulence or avirulence in maize was not correlated with a particular MLSA clade. The results support the hypothesis that genetic changes in the population of C. nebraskensis were correlated with recent area expansions of Goss's wilt.

中文翻译：

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与美国中北部近期和历史上 Goss's 枯萎病流行相关的 Clavibacter nebraskensis 菌株的遗传多样性和系统发育

由内布拉斯加州棒杆菌引起的高斯玉米枯萎病是美国和加拿大的一种重要病害。2000 年代中期戈斯枯萎病的重新出现以及随后该病害的传播可能是由于作物管理实践的变化以及病原体种群的变化所致。本研究的目的是确定与美国中北部近期和历史上 Goss's 枯萎病流行相关的 C. nebraskensis 菌株的遗传多样性和系统发育，测量采集期对种群结构的影响，并确定系统发育状态C. nebraskensis 的无毒菌株。使用多位点序列分析和分型来解决这些目标。对 atpD、dnaK 和 kdpA 序列的贝叶斯分析分离了 C. nebraskensis 来自其他三种 Clavibacter spp 的类型或参考菌株。本研究中使用的 125 株 C. nebraskensis 形成了一个单系分类群。确定了四个谱系。进化枝 I、II 和 IV 含有大量来自中西部上游的高毒株。进化枝 III 含有大量来自内布拉斯加州、科罗拉多州和南达科他州的菌株，这些菌株是在 1969 年至 1998 年间收集的。在内布拉斯加州和科罗拉多州历史性暴发的亚群与明尼苏达州最近暴发的亚群之间检测到了一个重要的亚结构。玉米中的毒力或无毒力与特定的 MLSA 进化枝无关。结果支持了以下假设：C. nebraskensis 种群的遗传变化与最近 Goss 枯萎病的面积扩张有关。