Data from: High levels of diversity and population structure in the potato late blight pathogen at the Mexico center of origin

Globally destructive crop pathogens often emerge by migrating out of their native ranges. These pathogens are often diverse at their center of origin, and may exhibit adaptive variation in the invaded range via multiple introductions from different source populations. However, source populations are generally unidentified or poorly studied compared to invasive populations. Phytophthora infestans, the causal agent of late blight, is one of the most costly pathogens of potato and tomato worldwide. Mexico is the center of origin and diversity of P. infestans and migration events out of Mexico have enormously impacted disease dynamics in North America and Europe. The debate over the origin of the pathogen, and population studies of P. infestans in Mexico, have focused on the Toluca Valley, whereas neighboring regions have been little studied. We examined the population structure of P. infestans across central Mexico, including samples from Michoacán, Tlaxcala, and Toluca. We found high levels of diversity consistent with sexual reproduction in Michoacán and Tlaxcala, and population subdivision that was strongly associated with geographical region. We determined that population structure in Central Mexico has contributed to diversity in introduced populations based on relatedness of U.S. clonal lineages to Mexican isolates from different regions. Our results suggest that P. infestans exists as a metapopulation in Central Mexico, and this population structure could be contributing to the repeated re-emergence of P. infestans in the U.S. and elsewhere.

具有全球毁灭性危害的作物病原物，往往通过脱离原生分布范围的扩散而暴发成灾。此类病原物在其起源中心通常具备较高的遗传多样性，且通过从不同源种群的多次引入，可在入侵区域产生适应性变异。然而相较于入侵种群，其源种群通常尚未被明确鉴定，或是研究程度较为薄弱。致病疫霉（Phytophthora infestans）是引发晚疫病的病原菌，也是全球范围内为害马铃薯与番茄造成经济损失最为惨重的病原物之一。墨西哥是致病疫霉的起源中心与多样性分布核心区域，其从墨西哥向外扩散的事件极大地影响了北美与欧洲的病害流行动态。此前围绕该病原物起源的学术争论，以及墨西哥境内致病疫霉的种群研究，均聚焦于托卢卡谷地（Toluca Valley），而邻近区域的相关研究则极为匮乏。本研究对墨西哥中部全域的致病疫霉种群结构展开了分析，采样区域涵盖米却肯州、特拉斯卡拉州与托卢卡谷地。研究发现，米却肯州与特拉斯卡拉州的菌株群体具备高度遗传多样性，且符合有性生殖的特征；同时种群分化与地理区域呈现显著相关性。通过比对美国克隆谱系与不同区域墨西哥菌株的亲缘关系，本研究证实墨西哥中部的种群结构是入侵种群遗传多样性的重要来源。研究结果表明，致病疫霉在墨西哥中部以集合种群（metapopulation）的形式存在，而这种种群结构可能是美国及其他地区致病疫霉反复暴发成灾的重要诱因。