Comparative study of nectar secretion and attractivity to bees of two lines of spring-type faba bean ( Vicia faba L var equina Steudel)J. Pierrea, J. Le Guenb, M.H. Pham Delèguec, J. Mesquidaa, R. Marilleauc and G. Morinb
a Laboratoire de zoologie, Centre de recherches de Rennes, Inra, BP 29, 35650 Le Rheu, France
b Station d'amélioration des plantes, Centre de recherches de Rennes, Inra, BP 29, 35650 Le Rheu, France
c Laboratoire de neurobiologie comparée des invertébrés, INRA-CNRS (Ura 1190), BP 23, 91440 Bures-sur-Yvette, France
Résumé - Two spring-type faba beans (D-27 self-fertile, D-23 non self-fertile) were observed in open field conditions for their nectar amount and sugar composition and their attractiveness to bees. Nectar amounts fluctuated according to the state of the flower, and in some cases also, the date of sampling and time of day. Nectar secretion of the D-27 line was four to six times higher than that of the D-23 line. High performance liquid chromatography analysis showed that the nectar was sucrose rich. There were substantial variations in nectar composition between plants and genotypes. D-23 was as attractive as D-27 to honeybees; in contrast, Bombus terrestris prefered D-27. Nevertheless, they paid a nearly equivalent proportion of robbing (non pollinating) visits to the two lines (D-23: 55%; D-27: 50%). In these conditions, the hole B terrestris made in the corolla to rob nectar, was used infrequently by honeybees. Most honeybees (68.6-76.2%) behaved 'legitimately' to probe nectar. The fact that the self-fertile (insect-independent) line is more attractive to bumblebees (because of its nectar production) is discussed.
Key words: Apis mellifera / Bombus / Vicia faba / nectar secretion / attractivity