INRA, Université Nice Côte d'Azur, CNRS, ISA, Sophia Antipolis, 06903, France.
Plant Protection Research Institute (PPRI), Hanoi, Vietnam.
Sci Rep. 2019 May 13;9(1):7313. doi: 10.1038/s41598-019-43812-4.
The soil-borne nematode Xiphinema index is closely linked to its main host, the grapevine, and presents a major threat to vineyards worldwide due to its ability to transmit Grapevine fanleaf virus (GFLV). The phylogeography of X. index has been studied using mitochondrial and microsatellite markers in samples from most regions of its worldwide distribution to reveal its genetic diversity. We first used the mitochondrial marker CytB and illustrated the low intraspecific divergence of this mainly meiotic parthenogenetic species. To generate a higher polymorphism level, we then concatenated the sequences of CytB and three mitochondrial markers, ATP6, CO1 and ND4, to obtain a 3044-bp fragment. We differentiated two clades, which each contained two well-supported subclades. Samples from the eastern Mediterranean and the Near and Middle East were grouped into three of these subclades, whereas the samples from the western Mediterranean, Europe and the Americas all belonged to the fourth subclade. The highest polymorphism level was found in the samples of one of the Middle and Near East subclades, strongly suggesting that this region contained the native area of the nematode. An east-to-west nematode dissemination hypothesis appeared to match the routes of the domesticated grapevine during Antiquity, presumably mainly dispersed by the Greeks and the Romans. Surprisingly, the samples of the western subclade comprised only two highly similar mitochondrial haplotypes. The first haplotype, from southern Iberian Peninsula, Bordeaux and Provence vineyards, exhibited a high microsatellite polymorphism level that suggests introductions dating from Antiquity. The second haplotype contained a highly predominant microsatellite genotype widespread in distant western countries that may be a consequence of the massive grapevine replanting following the 19-century phylloxera crisis. Finally, our study enabled us to draw a first scaffold of X. index diversity at the global scale.
根结线虫 Xiphinema index 与其主要宿主葡萄密切相关，由于其能够传播葡萄扇叶病毒 (GFLV)，因此对世界各地的葡萄园构成了重大威胁。已经使用线粒体和微卫星标记物对 X. index 的系统地理学进行了研究，这些标记物来自其全球分布的大多数地区的样本，以揭示其遗传多样性。我们首先使用线粒体标记物 CytB，并说明了这种主要减数分裂的部分孤雌生殖物种的低种内差异。为了产生更高的多态性水平，我们随后将 CytB 和三个线粒体标记物（ATP6、CO1 和 ND4）的序列串联起来，获得了一个 3044-bp 的片段。我们区分了两个进化枝，每个进化枝都包含两个支持良好的亚进化枝。来自东地中海以及近东和中东的样本被分为这三个亚进化枝，而来自西地中海、欧洲和美洲的样本都属于第四个亚进化枝。在中东和近东的一个亚进化枝的样本中发现了最高的多态性水平，强烈表明该地区包含了线虫的原生区。线虫从东向西传播的假说似乎与古代驯化葡萄的传播路线相吻合，可能主要是由希腊人和罗马人传播的。令人惊讶的是，西部亚进化枝的样本仅包含两个高度相似的线粒体单倍型。第一个单倍型来自伊比利亚半岛南部、波尔多和普罗旺斯的葡萄园，表现出高度的微卫星多态性，表明它是古代引入的。第二个单倍型包含一个在遥远的西方国家广泛分布的高度优势的微卫星基因型，这可能是 19 世纪根瘤蚜危机后大规模葡萄重植的结果。最后，我们的研究使我们能够在全球范围内绘制出 X. index 多样性的第一个支架。
