Department of Plant Pathology, University of California, Davis, CA, 95616, USA.
Ecologie Systematique Evolution, CNRS, Université Paris Sud, Orsay, F-91405, France.
Environ Microbiol. 2015 Aug;17(8):2824-40. doi: 10.1111/1462-2920.12789. Epub 2015 Mar 25.
The spread of aggressive fungal pathogens into previously non-endemic regions is a major threat to plant health and food security. Analyses of the spatial and genetic structure of plant pathogens offer valuable insights into their origin, dispersal mechanisms and evolution, and have been useful to develop successful disease management strategies. Here, we elucidated the genetic diversity, population structure and demographic history of worldwide invasion of the ascomycete Verticillium dahliae, a soil-borne pathogen, using a global collection of 1100 isolates from multiple plant hosts and countries. Seven well-differentiated genetic clusters were revealed through discriminant analysis of principal components (DAPC), but no strong associations between these clusters and host/geographic origin of isolates were found. Analyses of clonal evolutionary relationships among multilocus genotypes with the eBURST algorithm and analyses of genetic distances revealed that genetic clusters represented several ancient evolutionary lineages with broad geographic distribution and wide host range. Comparison of different scenarios of demographic history using approximate Bayesian computations revealed the branching order among the different genetic clusters and lineages. The different lineages may represent incipient species, and this raises questions with respect to their evolutionary origin and the factors allowing their maintenance in the same areas and same hosts without evidence of admixture between them. Based on the above findings and the biology of V. dahliae, we conclude that anthropogenic movement has played an important role in spreading V. dahliae lineages. Our findings have implications for the development of management strategies such as quarantine measures and crop resistance breeding.
侵袭性真菌病原体向以前非地方性区域的传播，对植物健康和粮食安全构成了重大威胁。对植物病原体的空间和遗传结构进行分析，为了解其起源、传播机制和进化提供了有价值的见解，并有助于制定成功的疾病管理策略。在这里，我们利用来自多个植物宿主和国家的 1100 个分离株的全球集合，阐明了土传病原体半知菌轮枝孢（Verticillium dahliae）在全球范围内的入侵的遗传多样性、种群结构和历史动态。通过主成分判别分析（DAPC）揭示了七个分化良好的遗传群，但这些群与分离株的宿主/地理起源之间没有很强的关联。通过 eBURST 算法对多基因座基因型的克隆进化关系进行分析和遗传距离分析表明，遗传群代表了几个具有广泛地理分布和广泛宿主范围的古老进化谱系。使用近似贝叶斯计算比较不同的种群历史情景表明了不同遗传群和谱系之间的分支顺序。不同的谱系可能代表初生种，这就提出了关于它们的进化起源以及在没有证据表明它们之间存在混合的情况下允许它们在同一地区和同一宿主中维持的因素的问题。基于上述发现和 V. dahliae 的生物学特性，我们得出结论，人为活动在传播 V. dahliae 谱系方面发挥了重要作用。我们的研究结果对检疫措施和作物抗性育种等管理策略的制定具有重要意义。
