Department of Plant Pathology and Weed Research, Agricultural Research Organization, Volcani Institute, Rishon LeZion, Israel.
The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Phytopathology. 2022 Jan;112(1):154-162. doi: 10.1094/PHYTO-04-21-0135-FI. Epub 2022 Jan 13.
A decade ago, shoot proliferation symptoms (i.e., witches' broom) in carrots were believed to be the cause of ' Phytoplasma' and infection, yet in recent years this association appeared to have weakened, and a closer association was found with the yet-unculturable, psyllid-transmitted Gram-negative bacterium ' Liberibacter solanacearum'. In Israel, carrots are grown throughout the year, yet shoot proliferation symptoms tend to appear only in mature plants and mostly in late spring to early summer. We hypothesized that factors such as plant age, temperature, and vector load, which vary during the year, have a critical effect on symptom development and examined these factors under controlled conditions. Here we show that young carrot seedlings are as prone as older plants to develop shoot proliferation symptoms after '. L. solanacearum' inoculation. Surprisingly, we found that the local '. L. solanacearum' haplotype was extremely sensitive to constant temperature of 30°C, which led to a significant reduction in bacterial growth and symptom development compared with 18°C, which was very conducive to symptom development. We have also found that inoculations with 10 or 20 psyllids per plant results in faster symptom development compared with inoculations with two psyllids per plant; however, the difference between vector loads in disease progress rate was not significant. These data provide important insights to the effects of plant age, growth temperature, and vector load on '. L. solanacearum' and its associated symptoms and further strengthen the notion that '. L. solanacearum' is the main responsible agent for carrot witches' broom in Israel.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
十年前，人们认为胡萝卜丛生症状（即“扫帚病”）是‘植原体’和感染的原因，但近年来，这种关联似乎减弱了，而与尚未培养的、由叶蝉传播的革兰氏阴性细菌‘甘蓝黄单胞菌’的关联更为密切。在以色列，全年都种植胡萝卜，但丛生症状往往只出现在成熟的植株上，而且大多出现在春末夏初。我们假设，植物年龄、温度和媒介负荷等因素在一年中会发生变化，对症状的发展有重要影响，并在受控条件下检查了这些因素。在这里，我们表明，年轻的胡萝卜幼苗在接种‘L. solanacearum’后，与较老的植物一样容易出现丛生症状。令人惊讶的是，我们发现当地的‘L. solanacearum’单倍型对 30°C 的恒温非常敏感，与非常有利于症状发展的 18°C 相比，这导致细菌生长和症状发展显著减少。我们还发现，与每株植物接种 2 只叶蝉相比，每株植物接种 10 或 20 只叶蝉会导致更快的症状发展；然而，在疾病进展速度方面，媒介负荷的差异并不显著。这些数据为植物年龄、生长温度和媒介负荷对‘L. solanacearum’及其相关症状的影响提供了重要的见解，并进一步加强了‘L. solanacearum’是以色列胡萝卜扫帚病的主要致病因子的观点。[公式：见正文] 版权所有©2022 作者。这是一个在 CC BY-NC-ND 4.0 国际许可下的开放获取文章。
