Anatomical modifications of xylem and phloem tissues of grapevine (Vitis vinifera) stems of shoots infected by the flavescence dorée phytoplasma (FDp) were first observed and described in the 1960s, but never quantified in detail. In this paper, we describe and quantify the impact of FDp on grapevine stem tissues, and relate it to the level of expression of symptoms and to cultivar‐specific FDp susceptibility. For this purpose, we measured and quantified the anatomical parameters of xylem and phloem tissues of a tolerant (Merlot) and a susceptible (Chardonnay) cultivar. For each cultivar, thin sections of eight shoots with symptoms from FDp‐infected grapevines, eight symptomless shoots from the same FDp‐infected grapevines, and eight symptomless shoots from symptomless grapevines (control) were compared. Results showed general inhibition of xylem growth and proliferation of phloem tissues (hyperplasia) with lack or irregular arrangement of the fibre‐sclereids in the axial phloem of the stems from shoots with symptoms, irrespective of the cultivar. Xylem vessels of infected Merlot shoots were partly occluded by tyloses and a higher number of smaller vessels were produced than in control plants. Thus, the anatomical responses confirmed the detrimental effect of FDp on stems of infected grapevine shoots, including impaired stem development and lack of periderm formation. Statistically significant differences were found between the two cultivars with different levels of susceptibility to FDp infection.

中文翻译：

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葡萄黄质植物原浆感染对葡萄树茎韧皮部和木质部的修饰

葡萄木质部和韧皮部组织的解剖修饰（葡萄）最早在1960年代观察到并描述了被黄褐藻（FDp）感染的新芽茎，但从未对其进行详细量化。在本文中，我们描述并量化了FDp对葡萄干组织的影响，并将其与症状的表达水平和特定品种的FDp敏感性相关。为此，我们测量并定量了耐性（梅洛特）和易感性（霞多丽）品种的木质部和韧皮部组织的解剖学参数。对于每个品种，比较了带有受FDp感染的葡萄的症状的8个芽的薄片，来自相同FDp感染的葡萄的8个无症状的芽和来自无症状的葡萄（对照）的8个无症状的芽。结果表明，有症状的芽的茎干轴突韧皮部缺乏或不规则排列的纤维状硬化菌，可普遍抑制韧皮部木质部的生长和增殖（增生），而与品种无关。被感染的梅鹿lot枝的木质部容器被酪醇部分地堵塞，并且与对照植物相比，产生了更多数量的较小容器。因此，解剖学反应证实了FDp对被感染的葡萄枝茎的有害作用，包括茎发育受损和缺乏皮层形成。在对FDp感染敏感性不同的两个品种之间发现了统计学上的显着差异。被感染的梅鹿lot枝的木质部容器被酪醇部分地堵塞，并且与对照植物相比，产生了更多数量的较小容器。因此，解剖学反应证实了FDp对被感染的葡萄枝茎的有害作用，包括茎发育受损和缺乏皮层形成。在对FDp感染敏感性不同的两个品种之间发现了统计学上的显着差异。被感染的梅鹿lot枝的木质部容器被酪醇部分地堵塞，并且与对照植物相比，产生了更多数量的较小容器。因此，解剖学反应证实了FDp对被感染的葡萄枝茎的有害作用，包括茎发育受损和缺乏皮层形成。在对FDp感染敏感性不同的两个品种之间发现了统计学上的显着差异。