Mycology and Nematology Genetic Diversity and Biology Laboratory, United States Department of Agriculture-Agricultural Research Service, Beltsville, MD.
Oak Ridge Institute for Science and Education, ARS Research Participation Program, Oak Ridge, TN.
Phytopathology. 2021 Jan;111(1):184-193. doi: 10.1094/PHYTO-06-20-0219-FI. Epub 2020 Nov 12.
Boxwood blight was first documented in Europe, prior to its recent colonization of North America, where it continues to have significant negative impacts on the ornamental industry. Due to near genetic uniformity in the two sister species of fungal plant pathogens that cause boxwood blight, understanding historical disease emergence and predicting future outbreaks is limited. The goal of this research was to apply population genomics to understand the role of pathogen diversification and migration in disease emergence. Specifically, we tested whether the primary pathogen species has remained genetically isolated from its European-limited sister species , while diversifying into clonal lineages that have migrated among continents. Whole-genome sequencing identified 1,608 single-nucleotide polymorphisms (SNPs) in 67 isolates from four continents and 1,017 SNPs in 13 isolates from Europe. Interspecific genetic differentiation and an absence of shared polymorphisms indicated lack of gene flow between the sister species. Tests for intraspecific genetic structure in identified four genetic clusters, three of which corresponded to monophyletic phylogenetic clades. Comparison of evolutionary divergence scenarios among the four genetic clusters using approximate Bayesian computation indicated that the two genetic clusters currently found in the United States were derived from different sources, one from the first genetic cluster found in Europe and the second from an unidentified population. Evidence for multiple introductions of this pathogen into the United States and intercontinental migration indicates that future introductions are likely to occur and should be considered in plant disease quarantine regulation.
黄杨枯萎病最早在欧洲有记录，随后在北美蔓延，对观赏植物产业造成了严重的负面影响。由于引起黄杨枯萎病的两种真菌病原菌在遗传上非常相似，因此了解疾病的历史爆发和预测未来的爆发受到限制。本研究旨在应用群体基因组学来理解病原体多样化和迁移在疾病爆发中的作用。具体来说，我们测试了主要病原菌是否一直与其在欧洲的姊妹种保持遗传隔离，同时是否向在各大洲迁移的克隆谱系多样化。全基因组测序在来自四大洲的 67 个分离株中鉴定出 1608 个单核苷酸多态性（SNP），在来自欧洲的 13 个分离株中鉴定出 1017 个 SNP。种间遗传分化和不存在共享多态性表明，姊妹种之间没有基因流。在 中进行的种内遗传结构测试表明存在四个遗传群，其中三个与单系系统发育枝相对应。使用近似贝叶斯计算比较四个遗传群之间的进化分歧情景表明，目前在美国发现的两个 遗传群来自不同的来源，一个来自欧洲的第一个遗传群，另一个来自一个未确定的种群。该病原体多次传入美国和洲际迁移的证据表明，未来可能会有更多的传入，应该在植物疾病检疫法规中加以考虑。
