Spartium junceum L. is a typical species of Mediterranean shrubland areas, also grown in gardens and parks as an ornamental. In recent years in Europe, S. junceum has been recurrently found to be infected by different subspecies and genotypes of the quarantine regulated bacterium Xylella fastidiosa (Xf). This work presents for the first time the anatomy of S. junceum plants that we found, by means of genetic and immunochemistry analysis, to be naturally infected by Xf subsp. multiplex ST87 (XfmST87) in Monte Argentario (Grosseto, Tuscany, Italy), a new outbreak area within the EU. Our anatomical observations showed that bacteria colonized exclusively the xylem conductive elements and moved horizontally to adjacent vessels through pits. Interestingly, a pink/violet matrix was observed with Toluidine blue staining in infected conduits indicating a high content of acidic polysaccharides. In particular, when this pink-staining matrix was observed, bacterial cells were either absent or degenerated, suggesting that the matrix was produced by the host plant as a defense response against bacterial spread. In addition, a blue-staining phenolic material was found in the vessels and, at high concentration, in the pits and inter-vessels. SEM micrographs confirmed that polysaccharide and phenolic components showed different structures, which appear to be related to two different morphologies: fibrillary and granular, respectively. Moreover, our LM observations revealed bacterial infection in xylem conductive elements of green shoots and leaves only, and not in those of other plant organs such as roots and flowers.

Spartium junceum L.是地中海灌丛区的典型品种，也生长于花园和公园作为观赏植物。近年来，在欧洲，反复发现S.junceum被检疫性规定的细菌Xylella fastidiosa (Xf) 的不同亚种和基因型感染。这项工作首次展示了我们通过遗传和免疫化学分析发现的S.junceum植物的解剖结构，这些植物会被 Xf 亚种自然感染。多路复用ST87 (XfmST87) 位于 Monte Argentario（意大利托斯卡纳的格罗塞托），这是欧盟内的一个新爆发区。我们的解剖观察表明，细菌仅在木质部导电元件中定殖，并通过凹坑水平移动到相邻的血管。有趣的是，在感染的导管中用甲苯胺蓝染色观察到粉红色/紫色基质，表明酸性多糖含量高。特别是，当观察到这种粉红色的基质时，细菌细胞要么不存在，要么退化，这表明基质是由宿主植物产生的，作为对细菌传播的防御反应。此外，在容器中以及在凹坑和容器间发现高浓度的蓝色酚醛材料。SEM显微照片证实多糖和酚类成分显示出不同的结构，这似乎与两种不同的形态有关：纤维状和颗粒状。此外，我们的 LM 观察显示，细菌感染仅存在于绿芽和叶子的木质部导电元件中，而其他植物器官（如根和花）中则没有。