PNAS:基因分析推测马铃薯晚疫病病原体的起源

对来自全世界的马铃薯晚疫病病原体种群的一项遗传分析揭示出了这种病原体很可能起源于墨西哥，而不是起源于此前分析提示的南美洲安第斯山。这项研究是由美国农业部农业研究局园艺作物研究实验室等处组成的一个国际研究组完成的。相关文章发表于2014年6月2日的《PNAS》杂志上。

马铃薯晚疫病是由马铃薯晚疫病菌(Phytophthora infestans)导致的，这是一种真菌样的卵菌，在很大程度上造成了19世纪40年代的欧洲马铃薯饥荒。最初来自美洲的马铃薯晚疫病菌在全世界每年导致了估计约60亿美元的农作物损失。

Niklaus J. Grünwald及其同事测定了来自全世界100多个马铃薯晚疫病菌样本以及4个与马铃薯晚疫病菌亲缘密切的物种的4个基因，从而推测出这个病原体的起源。比较了这4个被测序基因上的多个位点的一项贝叶斯概率分析揭示出了这5种疫霉菌物种的祖先关系，指向了墨西哥起源。

这项比较还提供了证据表明马铃薯晚疫病菌很可能从墨西哥迁徙到了安第斯山。这组作者说，了解马铃薯晚疫病菌的起源提供了对这种病原体的遗传多样性以及适应不同环境的见解，这些都可以为培育抗虫害作物和管理这种疾病的工作提供信息。

原文摘要：

The Irish potato famine pathogen Phytophthora infestansoriginated in central Mexico rather than the Andes

erica M. Goss, Javier F. Tabima, David E. L. Cooke, Silvia Restrepo, William E. Fry,Gregory A. Forbes, Valerie J. Fieland, Martha Cardenas and Niklaus J. Grünwald

Phytophthora infestans is a destructive plant pathogen best known for causing the disease that triggered the Irish potato famine and remains the most costly potato pathogen to manage worldwide. Identification of P. infestan’s elusive center of origin is critical to understanding the mechanisms of repeated global emergence of this pathogen. There are two competing theories, placing the origin in either South America or in central Mexico, both of which are centers of diversity of Solanum host plants. To test these competing hypotheses, we conducted detailed phylogeographic and approximate Bayesian computation analyses, which are suitable approaches to unraveling complex demographic histories. Our analyses used microsatellite markers and sequences of four nuclear genes sampled from populations in the Andes, Mexico, and elsewhere. To infer the ancestral state, we included the closest known relatives Phytophthora phaseoli, Phytophthora mirabilis, and Phytophthora ipomoeae, as well as the interspecific hybrid Phytophthora andina. We did not find support for an Andean origin of P. infestans; rather, the sequence data suggest a Mexican origin. Our findings support the hypothesis that populations found in the Andes are descendants of the Mexican populations and reconcile previous findings of ancestral variation in the Andes. Although centers of origin are well documented as centers of evolution and diversity for numerous crop plants, the number of plant pathogens with a known geographic origin are limited. This work has important implications for our understanding of the coevolution of hosts and pathogens, as well as the harnessing of plant disease resistance to manage late blight.

作者：生物帮