Abstract

Infection with the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) is suspected to cause severe damage in carrot leading to high carrot weight loss. This study investigates three main aspects: (i) whether there is a reduction of carrot root weight under field conditions due to Lso infection; (ii) the correlation between Lso infection rate in carrot plants and occurrence of the psyllid Trioza apicalis as the known vector for Lso in carrot, and (iii) the comparison between symptoms described in literature and observed symptoms associated with Lso infection. Therefore, field surveys were conducted from 2018 to 2021 on organically managed carrot fields in Lower Saxony, Germany. Two Rebell orange sticky traps were placed per field replaced on a weekly basis. Captured T. apicalis were morphologically identified and counted. Carrot plant samples were collected from T. apicalis infested fields. Discolouration of foliage and further symptoms on carrots were investigated. For detection of Lso in carrot plants and psyllids, the samples were analysed using PCR. The infection rate of carrot plants varied between 2.5% and 80% per field with low abundance of T. apicalis. Of the asymptomatic plants, 39.4% were infected with Lso, while 80.9% of the symptomatic plants were infected with Lso. The weight of Lso-positive carrot samples was not significantly reduced compared to Lso-negative samples. No economically relevant losses of carrot yield were reported by farmers participating in this study. This indicates that there was no effect of Lso infection on carrot root weight during this study. Of the symptoms associated with a Lso infection in carrots, only leaf discolouration could be confirmed. Overall, the bacterium is present in organically grown carrot plants in Lower Saxony but no major carrot root weight losses were observed.

中文翻译：

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德国‘Candidatus Liberibacter solanacearum’感染对胡萝卜根重的影响

摘要

细菌“ Candidatus Liberibacter solanacearum”（Lso）的感染被怀疑会对胡萝卜造成严重损害，导致胡萝卜重量大幅减轻。本研究主要调查三个方面：（i）田间条件下胡萝卜根重是否因 Lso 感染而减少； (ii) 胡萝卜植物中的 Lso 感染率与作为胡萝卜中已知的 Lso 载体的木虱Trioza apicalis的出现之间的相关性，以及 (iii) 文献中描述的症状与观察到的与 Lso 感染相关的症状之间的比较。因此，2018年至2021年对德国下萨克森州的有机管理胡萝卜田进行了实地调查。每个田地放置两个 Rebell 橙色粘性陷阱，每周更换一次。对捕获的顶端毛虫进行形态学鉴定和计数。胡萝卜植物样品是从T. apicalis感染的田地采集的。研究了胡萝卜叶子的变色和进一步的症状。为了检测胡萝卜植物和木虱中的 Lso，使用 PCR 分析了样品。每块田间胡萝卜植物的感染率在 2.5% 至 80% 之间变化，其中T. apicalis丰度较低。在无症状植物中，39.4%感染了Lso，而有症状植物中80.9%感染了Lso。与 Lso 阴性样品相比，Lso 阳性胡萝卜样品的重量没​​有显着减少。参与这项研究的农民没有报告与经济相关的胡萝卜产量损失。这表明在本研究中 Lso 感染对胡萝卜根重量没有影响。在与胡萝卜 Lso 感染相关的症状中，只能确认叶子变色。总体而言，这种细菌存在于下萨克森州有机种植的胡萝卜植物中，但没有观察到胡萝卜根重量大幅下降。