CBGP, INRA, CIRAD, IRD, Montpellier SupAgro, University Montpellier, Montpellier, France.
INRA, UMR1334 AGAP, F-34398, Montpellier, France.
Sci Rep. 2018 Oct 23;8(1):15628. doi: 10.1038/s41598-018-33957-z.
We sampled ca 2500 specimens of Philaenus spumarius (Hemiptera: Aphrophoridae) throughout Corsica without a priori knowledge on the presence of symptoms on plants. We screened 448 specimens for the presence of Xylella fastidiosa (Xf) using qPCR and a custom nested PCR. qPCR appeared versatile and under-estimated the prevalence of Xf. Nested PCR showed that Xf was present in all populations. Molecular results were validated by prediction on the distribution of Xf made from tests conducted on plants, which shows the pertinence of using vectors in risk assessment studies. Xf was detected in tenerals and adults. Thus, P. spumarius could acquire Xf from its host plant, mostly Cistus monspeliensis in Corsica, which may act as reservoir for the next season. This contrasts with other observations and suggests that management strategies may have to be adapted on a case-by-case basis. At least two genetic entities and several variants of Xf not yet identified on plants were present in the insects, which suggests ancient introductions of Xf and a probable underestimation of the current diversity of the strains present in Corsica. Interestingly 6% of the specimens carried two subspecies of Xf. Studies are required to better characterize the strains present in Corsica and to determine how the disease was introduced, spread and why no sign of a potential epidemic was detected earlier. This study shows that, when sensitive enough methods are implemented, spittlebugs (and more specifically P. spumarius for which species distribution modelling shows it could be a good sentinel for Europe) can be used to predict and better assess the exact distribution of Xf. Furthermore, Xf multiply only in their foregut and does not become circulative, which facilitates its detection.
我们在没有事先了解植物是否出现症状的情况下，在科西嘉岛采集了约 2500 份 Philaenus spumarius（半翅目：叶蝉科）标本。我们使用 qPCR 和定制的巢式 PCR 对 448 个标本进行了 Xylella fastidiosa（Xf）的存在筛查。qPCR 表现出多功能性，并低估了 Xf 的流行率。巢式 PCR 显示 Xf 存在于所有种群中。分子结果通过在植物上进行的测试对 Xf 分布的预测进行了验证，这表明在风险评估研究中使用媒介物的相关性。Xf 在若虫和成虫中均有发现。因此，P. spumarius 可以从其宿主植物（科西嘉的主要是 Cistus monspeliensis）中获得 Xf，这可能是下一季的储源。这与其他观察结果相反，表明管理策略可能需要根据具体情况进行调整。在昆虫中存在至少两种遗传实体和几种尚未在植物上鉴定的 Xf 变体，这表明 Xf 的早期引入和对科西嘉当前存在菌株多样性的可能低估。有趣的是，6%的标本携带两种 Xf 亚种。需要进行研究以更好地描述科西嘉存在的菌株，并确定疾病是如何传入、传播的，以及为什么早些时候没有发现潜在流行的迹象。这项研究表明，当采用足够敏感的方法时，可以使用沫蝉（特别是 P. spumarius，物种分布模型表明它可能是欧洲的良好哨兵）来预测和更好地评估 Xf 的确切分布。此外，Xf 只能在其前肠中繁殖，不会循环，这便于其检测。
