Phytophthora austrocedri is a recently invasive pathogen causing widespread mortality of the ecologically important native conifer, Juniperus communis, in northern Britain. Observations of disease symptoms at severely infected woodlands revealed the presence of individual, apparently healthy trees in areas of high mortality. This study was undertaken to test the hypothesis that these ‘survivor’ trees have greater resistance to P. austrocedri. Rooted cuttings were obtained from seventeen putatively resistant J. communis clones at two heavily infected natural woodlands. Inoculation of excised stems from three putatively resistant clones with P. austrocedri provided initial data to support the hypothesis of resistance. A larger trial was conducted in which whole J. communis plants representing seventeen putatively resistant clones and a known susceptible clone were inoculated with two isolates of P. austrocedri. This trial revealed variation in resistance, with at least six clones exhibiting a high degree of resistance to the pathogen. One surprising finding given the lack of genetic diversity in UK P. austrocedri isolates was that one of the clones was resistant to one isolate and susceptible to the other, warranting further investigation. The next steps are to ascertain whether this natural resistance in J. communis is heritable and exploitable for population recovery.

中文翻译：

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杜松对 Phytophthora austrocedri 天然抗性的证据

Phytophthora austrocedri 是最近入侵的病原体，导致英国北部具有重要生态意义的本地针叶树杜松广泛死亡。对严重受感染林地疾病症状的观察表明，在高死亡率地区存在个体、明显健康的树木。进行这项研究是为了检验这些“幸存者”树木对 P. austrocedri 具有更大抗性的假设。从两个严重感染的天然林地中的 17 个推定抗性 J.communis 克隆中获得带根插条。从三个推定的抗性克隆中接种切离的茎与南方假单胞菌提供了支持抗性假设的初始数据。进行了一项更大的试验，其中整个 J. 代表 17 个推定抗性克隆和已知的易感克隆的共生植物用两种 P. austrocedri 分离株接种。该试验揭示了耐药性的变化，至少有六个克隆对病原体表现出高度的耐药性。鉴于英国 P. austrocedri 分离株缺乏遗传多样性，一个令人惊讶的发现是其中一个克隆对一种分离株具有抗性，而对另一种分离株易感，值得进一步调查。接下来的步骤是确定 J.communis 的这种自然抵抗力是否可遗传并可用于种群恢复。鉴于英国 P. austrocedri 分离株缺乏遗传多样性，一个令人惊讶的发现是其中一个克隆对一种分离株具有抗性，而对另一种分离株易感，值得进一步调查。接下来的步骤是确定 J.communis 的这种自然抵抗力是否可遗传并可用于种群恢复。鉴于英国 P. austrocedri 分离株缺乏遗传多样性，一个令人惊讶的发现是，其中一个克隆对一种分离株具有抗性，而对另一种分离株易感，值得进一步调查。接下来的步骤是确定 J.communis 的这种自然抵抗力是否可遗传并可用于种群恢复。