Instituto Nacional de Tecnología Agropecuaria (INTA), Estación Experimental Agropecuaria La Consulta, La Consulta, M5567 Mendoza, Argentina.
Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, M5502 JMA Mendoza, Argentina.
J Exp Biol. 2019 Jan 28;222(Pt 2):jeb189910. doi: 10.1242/jeb.189910.
The honey bee is the most frequently used species in pollination services for diverse crops. In onion crops (), however, bees avoid visiting certain varieties, being attracted differently to male sterile (MS) and fertile (OP) lines. These differences might be based on the phenolic profiles of the cultivars' nectars. To understand the relationship between nectar composition and pollinator attraction to different onion lines, we tested sensory and cognitive abilities and palatability in honey bees exposed to MS and OP onion nectars and sugar solutions mimicking them. We evaluated the proboscis extension response (PER) after antennal contact (unconditioned response) to MS or OP onion nectars, finding no statistical differences, which indicates similar gustatory perception for the two nectars. We also performed food uptake assays to test palatability of different artificial nectars, considering their flavonoids and potassium content. The presence of potassium decreased the palatability of the artificial nectars. Finally, we evaluated the bees' cognitive abilities when the reward (unconditioned stimulus) offered during conditioning PER assays presents differences in composition. We found that potassium by itself impaired learning; however, such impairment was even higher when naringenin and quercetin were added in the unconditioned stimulus (MS nectar mimic). Interestingly, potassium together with luteolin (OP nectar mimic) improved learning. Our study demonstrates that the differences in the nectars' flavonoid profiles combined with their high potassium content could explain the previously reported differences in attractiveness between onion lines, suggesting an important role of nectar compounds other than sugars for the attractiveness of flowers to pollinators.
蜜蜂是授粉服务中最常被用于多种作物的物种。然而，在洋葱作物中，蜜蜂会避免访问某些品种，而是对雄性不育（MS）和可育（OP）系产生不同的吸引力。这些差异可能基于品种花蜜的酚类谱。为了了解不同洋葱系的花蜜成分与传粉者吸引力之间的关系，我们测试了暴露于 MS 和 OP 洋葱花蜜和模仿它们的糖溶液中的蜜蜂的感觉和认知能力以及可接受性。我们评估了触角接触后的触角延伸反应（PER）（无条件反应）对 MS 或 OP 洋葱花蜜的反应，发现没有统计学差异，这表明两种花蜜的味觉感知相似。我们还进行了食物摄取测定，以测试不同人工花蜜的可接受性，同时考虑其类黄酮和钾含量。钾的存在降低了人工花蜜的可接受性。最后，当条件 PER 测定中提供的奖励（无条件刺激）在组成上存在差异时，我们评估了蜜蜂的认知能力。我们发现钾本身会损害学习能力；然而，当 unconditioned stimulus (MS 花蜜模拟物) 中添加柚皮素和槲皮素时，这种损害甚至更高。有趣的是，当与木樨草素（OP 花蜜模拟物）一起使用时，钾可以改善学习。我们的研究表明，花蜜中类黄酮谱的差异以及它们的高钾含量可以解释先前报道的洋葱系之间吸引力的差异，这表明花蜜化合物对花朵对传粉者的吸引力除了糖之外还有重要作用。
