INRA, UMR1136, INRA, Université de Lorraine, Interactions Arbres- Micro- organismes, IFR110 EFABA, Centre INRA de Nancy, 54280 Champenoux, France.
Phytopathology. 2013 Feb;103(2):190-9. doi: 10.1094/PHYTO-05-12-0116-R.
Alder decline caused by Phytophthora alni has been one of the most important diseases of natural ecosystems in Europe during the last 20 years. The emergence of P. alni subsp. alni -the pathogen responsible for the epidemic-is linked to an interspecific hybridization event between two parental species: P. alni subsp. multiformis and P. alni subsp. uniformis. One of the parental species, P. alni subsp. uniformis, has been isolated in several European countries and, recently, in North America. The objective of this work was to assess the level of genetic diversity, the population genetic structure, and the putative reproduction mode and mating system of P. alni subsp. uniformis. Five new polymorphic microsatellite markers were used to contrast both geographical populations. The study comprised 71 isolates of P. alni subsp. uniformis collected from eight European countries and 10 locations in North America. Our results revealed strong differences between continental populations (Fst = 0.88; Rst = 0.74), with no evidence for gene flow. European isolates showed extremely low genetic diversity compared with the North American collection. Selfing appears to be the predominant mating system in both continental collections. The results suggest that the European P. alni subsp. uniformis population is most likely alien and derives from the introduction of a few individuals, whereas the North American population probably is an indigenous population.
在过去的 20 年中，由 Phytophthora alni 引起的桤木衰退已经成为欧洲自然生态系统中最重要的疾病之一。P. alni subsp. alni 的出现——导致该流行病的病原体——与两个亲本物种之间的种间杂交事件有关：P. alni subsp. multiformis 和 P. alni subsp. uniformis。亲本物种之一 P. alni subsp. uniformis 已在几个欧洲国家和最近在北美被分离出来。本研究的目的是评估 P. alni subsp. uniformis 的遗传多样性水平、种群遗传结构以及可能的繁殖方式和交配系统。使用 5 个新的多态性微卫星标记来对比地理种群。该研究包括从欧洲八个国家和北美 10 个地点收集的 71 个 P. alni subsp. uniformis 分离株。研究结果显示，大陆种群之间存在强烈差异（Fst = 0.88；Rst = 0.74），没有证据表明基因流。与北美采集的样本相比，欧洲分离株的遗传多样性极低。自交似乎是两种大陆群体中主要的交配系统。结果表明，欧洲的 P. alni subsp. uniformis 种群很可能是外来的，并且是由少数个体引入的，而北美的种群可能是本地种群。
