In 2012, Italian kiwifruit orchards were hit by a serious root disease of unknown aetiology (kiwifruit decline, KD) that still causes extensive damage to the sector. While waterlogging was soon observed to be associated with its outbreak, the putative role of soil microbiota remains unknown. This work investigates the role of these two factors in the onset of the disease. Historical rainfall data were analysed to identify changes that might explain KD outbreak and mimic the flooding conditions required to reproduce the disease in a controlled environment. A greenhouse experiment was thus designed, and vines were grown in either unsterilized (U) or sterilized (S) soil collected from KD-affected orchards, and subjected (F) or not (N) to artificial flooding. Treatments were compared in terms of mortality rate, growth, and tissue modifications. KD symptoms were only displayed by FU-treated vines, with an incidence of 90%. Ultrastructural observations detected tyloses and fibrils in the xylem vessels of all plants, irrespective of the treatment. Phytopythium vexans and Phytopythium chamaehyphon, isolated from roots of FU plants, emerged as the associated microorganisms. We succeeded in reproducing KD under controlled conditions and confirmed its association with both waterlogging and soil-borne microorganism(s).

中文翻译：

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猕猴桃衰败病原学研究：土传病原菌与内涝的相互作用

2012 年，意大利猕猴桃果园遭受了一种病因不明的严重根病（猕猴桃衰退，KD），至今仍对该部门造成广泛破坏。虽然很快观察到内涝与其爆发有关，但土壤微生物群的假定作用仍然未知。这项工作调查了这两个因素在疾病发作中的作用。分析历史降雨数据以确定可能解释 KD 爆发的变化，并模拟在受控环境中重现该疾病所需的洪水条件。因此设计了一个温室实验，葡萄藤生长在从受 KD 影响的果园收集的未消毒 (U) 或已消毒 (S) 土壤中，并进行 (F) 或不 (N) 人工洪水。在死亡率、生长和组织修饰方面对治疗进行了比较。KD 症状仅由 FU 处理的葡萄藤表现出来，发生率为 90%。超微结构观察在所有植物的木质部血管中检测到 tyloses 和原纤维，与处理无关。从 FU 植物的根中分离出的 Phytopythium v​​exans 和 Phytopythium chamaehyphon 作为相关微生物出现。我们成功地在受控条件下繁殖了 KD，并证实了它与涝渍和土壤传播微生物的关联。