Caractérisation de Signaux Chimiques Impliqués dans les Relations Plantes-Abeilles Domestiques

Abstract

To characterize plant chemicals cueing honeybees preferences between sunflower genotypes selected to produce hybrid seeds, combined behavioral and chemical analyses were undertaken. From observations of the foraging behavior under field conditions, bees' preferences between female and male parent lines were shown. Since bees' attraction to plants is based upon an associative conditioning between food, provided by nectar and pollen, and plant volatiles, these components were compared between genotypes. Sugar composition of nectars was analyzed by gas chromatography: glucose, fructose and sucrose were identified, with sucrose inducing bees' preferences. Pollen production was quantified on parent lines and resulting hybrid varieties, using a coulter-counter device. Differences among parent lines and heredity effect were found. However, there were strong interaction between parental lines and high variability within genotypes. Pollenkitt analysis, using thin layer chromatography was undertaken to separate the main classes of lipids (hydrocarbons, sterols, mono-, di- and triglycerids). Fatty acids composition was analyzed by gas chromatography, the main components being two unsaturated fatty acids. Comparison of volatile components collected by air-entrainment method showed differences between male and female genotypes. Discriminative components were limited to 10% of the volatile blends and were identified by coupled gas chromatography-mass spectrometry.