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. 2018 Mar 13;9(1):31.
doi: 10.3390/insects9010031.

Honeybees Tolerate Cyanogenic Glucosides from Clover Nectar and Flowers

Antoine Lecocq, Amelia A Green, Érika Cristina Pinheiro De Castro, Carl Erik Olsen, Annette B Jensen, Mika Zagrobelny

Honeybees Tolerate Cyanogenic Glucosides from Clover Nectar and Flowers

Antoine Lecocq et al. Insects. .

Abstract

Honeybees (Apis mellifera) pollinate flowers and collect nectar from many important crops. White clover (Trifolium repens) is widely grown as a temperate forage crop, and requires honeybee pollination for seed set. In this study, using a quantitative LC-MS (Liquid Chromatography-Mass Spectrometry) assay, we show that the cyanogenic glucosides linamarin and lotaustralin are present in the leaves, sepals, petals, anthers, and nectar of T. repens. Cyanogenic glucosides are generally thought to be defense compounds, releasing toxic hydrogen cyanide upon degradation. However, increasing evidence indicates that plant secondary metabolites found in nectar may protect pollinators from disease or predators. In a laboratory survival study with chronic feeding of secondary metabolites, we show that honeybees can ingest the cyanogenic glucosides linamarin and amygdalin at naturally occurring concentrations with no ill effects, even though they have enzyme activity towards degradation of cyanogenic glucosides. This suggests that honeybees can ingest and tolerate cyanogenic glucosides from flower nectar. Honeybees retain only a portion of ingested cyanogenic glucosides. Whether they detoxify the rest using rhodanese or deposit them in the hive should be the focus of further research.

Keywords: clover (Trifolium repens); cyanogenic glucoside; honeybee (Apis mellifera); linamarin; nectar.

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Conflict of interest statement

The authors declare no conflicting interests.

Figures

Figure 1
Figure 1
Cyanogenic glucosides are found by LC-MS in leaves, flowers and nectar of white clover. (a) A single Trifolium repens flower, separated into sepals, petals and reproductive parts (stamens and pistils combined). (b) Linamarin (green) and lotaustralin (blue) concentrations (determined by LC-MS) in leaves and flower parts (sepals, petals, combined reproductive parts, anthers) of T. repens; four samples for each. (c) Linamarin (green) and lotaustralin (blue) concentrations (determined by LC-MS) in nectar of T. repens; four samples. Error bars in (b,c) show standard error. (d) Representative Extracted Ion Chromatogram (EIC) from LC-MS showing linamarin (green, [M + Na]+ = 270) and lotaustralin (blue, [M + Na]+ = 284) in nectar.
Figure 2
Figure 2
Survival plot for bees in the control, amygdalin and linamarin treatments. Amygdalin treatments in red, Linamarin in green and Control represented by a black line. Concentrations of 1 ng/μL shown by a dashed line, 10 ng/μL shown by dots and dashes and 100 ng/μL a full line.
See this image and copyright information in PMC

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