Funding information Forestry Commission Abstract Phytophthora austrocedri is a recently invasive soilborne pathogen which is causing widespread mortality of Juniperus communis in northern Britain. The pathways by which a single genotype of P. austrocedri has spread to infect such a geographically dispersed range of woodland sites within a relatively short timeframe are unknown. This study examined the detectability of P. austrocedri in soil and water within infected J. communis woodland using qPCR to gain a better understanding of the pathogen's key mechanisms of spread. A Phytophthora metabarcoding method was also applied to investigate the wider diversity of Phytophthora species present in water at one of the sites. qPCR analyses of P. austrocedri in soil samples at a J. communis woodland exhibiting low-to-moderate levels of disease suggested a slow natural spread of the pathogen in soil, requiring high moisture conditions. However, the ubiquity of P. austrocedri DNA in soil samples collected across a heavily infected J. communis site suggests that once established at a site the pathogen can be spread readily in soil locally, most likely vectored by animal movements and/or human activities. The hypothesis that P. austrocedri is aerially transmitted in rainwater was not adequately proven, and an alternative hypothesis for the widespread distribution of the pathogen on J. communis in northern Britain is presented. Metabarcoding identified DNA from a diverse range of Phytophthora species in river and rainwater samples although the main target pathogen, P. austrocedri, was not amplified which disagreed with some of the qPCR findings. Possible reasons for this are discussed.

中文翻译：

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Metabarcoding 揭示受感染杜松林地中 Phytophthora austrocedri 的检测和传播以及相关疫霉的多样性

资金信息 林业委员会 摘要 Phytophthora austrocedri 是一种最近侵入的土壤传播病原体，它导致英国北部杜松普遍死亡。尚不清楚单一基因型 P. austrocedri 在相对较短的时间范围内传播以感染地理上分散的林地范围的途径。本研究使用 qPCR 检查了受感染的 J.communis 林地土壤和水中的 P. austrocedri 的可检测性，以更好地了解病原体的关键传播机制。还应用了疫霉元条形码方法来研究其中一个地点水中存在的疫霉属物种的更广泛多样性。J. 土壤样品中 P. austrocedri 的 qPCR 分析。表现出低至中度疾病水平的共生林地表明病原体在土壤中自然传播缓慢，需要高湿度条件。然而，在严重感染的 J.communs 站点收集的土壤样本中 P. austrocedri DNA 的普遍存在表明，一旦在一个站点建立，病原体就可以很容易地在当地土壤中传播，最有可能通过动物运动和/或人类活动传播。P. austrocedri 在雨水中通过空气传播的假设没有得到充分证实，并且提出了一种关于病原体在英国北部 J.communs 上广泛分布的替代假设。Metabarcoding 鉴定了来自河流和雨水样本中多种疫霉属物种的 DNA，尽管主要目标病原体 P. austrocedri，未扩增，这与一些 qPCR 结果不一致。讨论了可能的原因。