Department of Agricultural and Food Sciences, Alma Mater Studiorum - University of Bologna, viale G. Fanin 44, Bologna, 40127, Italy.
Faculty of Science and Technology, Free University of Bozen-Bolzano, Piazza Università 5, Bolzano, 39100, Italy.
ISME J. 2019 Apr;13(4):847-859. doi: 10.1038/s41396-018-0319-2. Epub 2018 Nov 30.
Honeybees are well recognised for their key role in plant reproduction as pollinators. On the other hand, their activity may vector some pathogens, such as the bacterium Erwinia amylovora, the causative agent of fire blight disease in pomaceous plants. In this research, we evaluated whether honeybees are able to discriminate between healthy and E. amylovora-infected flowers, thus altering the dispersal of the pathogen. For this reason, honeybees were previously trained to forage either on inoculated or healthy (control) apple flower. After the training, the two honeybee groups were equally exposed to inoculated and control flowering apple plants. To assess their preference, three independent methods were used: (1) direct count of visiting bees per time frame; (2) incidence on apple flowers of a marker bacterium (Pantoea agglomerans, strain P10c) carried by foragers; (3) quantification of E. amylovora populations in the collected pollen loads, proportional to the number of visits to infected flowers. The results show that both honeybee groups preferred control flowers over inoculated ones. The characterisation of volatile compounds released by flowers revealed a different emission of several bioactive compounds, providing an explanation for honeybee preference. As an unexpected ecological consequence, the influence of infection on floral scent increasing the visit rate on healthy flowers may promote a secondary bacterial spread.
蜜蜂作为传粉者，其在植物繁殖中的关键作用得到了广泛认可。另一方面，它们的活动可能会传播一些病原体，如细菌 Erwinia amylovora，这是蔷薇科植物火疫病的病原体。在这项研究中，我们评估了蜜蜂是否能够区分健康花和感染 E. amylovora 的花，从而改变病原体的传播。为此，蜜蜂在之前接受了训练，要么在接种花上觅食，要么在健康（对照）苹果花上觅食。训练后，两组蜜蜂都平等地接触到接种和对照开花的苹果树。为了评估它们的偏好，使用了三种独立的方法：（1） 每个时间框架内访问蜜蜂的直接计数；（2） 由觅食者携带的标记细菌（ Pantoea agglomerans ，菌株 P10c）在苹果花上的发病率；（3） 在收集的花粉负荷中定量 E. amylovora 种群，与访问感染花朵的次数成正比。结果表明，两组蜜蜂都更喜欢对照花而不是接种花。对花释放的挥发性化合物的特征分析显示，几种生物活性化合物的释放存在差异，这为蜜蜂的偏好提供了解释。作为一个意外的生态后果，感染对花香的影响增加了对健康花朵的访问率，可能会促进二次细菌传播。
