Abstract

Xylella fastidiosa (Xf) Wells, Raju et al., 1986 is a bacterium that causes plant diseases in the Americas. In Europe, it was first detected on the Salento Peninsula (Italy), where it was found to be associated with the olive quick decline syndrome. Here, we present the results of the first tree-ring study of infected and uninfected olive trees (Olea europaea L.) of two different cultivars, one resistant and one susceptible, to establish the effects induced by the spread of the pathogen inside the tree. Changes in wood anatomical characteristics, such as an increase in the number of vessels and in ring width, were observed in the infected plants of both the cultivars Cellina di Nardò (susceptible to Xf infection) and Leccino (resistant to Xf infection). Thus, whether infection affects the mortality of the tree or not, the tree shows a reaction to it. The presence of occlusions was detected in the wood of both 4-year-old branches and the tree stem core. As expected, the percentage of occluded vessels in the Xf-susceptible cultivar Cellina di Nardò was significantly higher than in the Xf-resistant cultivar Leccino. The δ ¹⁸O of the 4-year-old branches was significantly higher in infected trees of both cultivars than in noninfected trees, while no variations in δ ¹³C were observed. This suggests a reduction in leaf transpiration rates during infection and seems to be related to the occlusions observed in rings of the 4-year-old branches. Such occlusions can determine effects at leaf level that could influence stomatal activity. On the other hand, the significant increase in the number of vessels in infected trees could be related to the tree’s attempt to enhance water conductivity in response to the pathogen-induced vessel occlusions.

中文翻译：

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感染了Xylella fastidiosa的橄榄树中环的宽度，血管数和δ18O的增加。

摘要

Xylella fastidiosa（Xf）Wells，Raju等人，1986年，是一种在美洲引起植物病害的细菌。在欧洲，它是在意大利的Salento半岛上首次发现的，与橄榄快速衰退综合征有关。在这里，我们介绍了两种抗病和易感的两个不同品种的受感染和未感染橄榄树（油橄榄）的第一个年轮研究的结果，以确定由病原体在树内传播引起的影响。在Cellina diNardò（易受Xf感染）和Leccino（对Xf的抗性）两个品种的受感染植物中均观察到木材解剖学特征的变化，例如血管数量和环宽度的增加。Xf感染）。因此，无论感染是否影响树木的死亡率，树木都对其产生反应。在4岁的树枝和树茎核心的木材中都检测到了遮挡物。正如预期的那样，对Xf敏感的栽培品种Cellina diNardò中的闭塞血管百分比显着高于对Xf耐药的Leccino栽培品种。该δ ¹⁸ 4年生枝条的O的两品种比未感染的树木被感染的树木显著较高，而δ没有变化¹³观察到C。这表明感染期间叶片蒸腾速率降低，并且似乎与在4岁树枝的环中观察到的闭塞有关。此类阻塞可以确定可能影响气孔活动的叶片水平的影响。另一方面，受感染树木中血管数量的显着增加可能与树木响应病原体诱导的血管阻塞而试图提高水的电导率有关。