Floral volatiles may influence honey bee visitations in oilseed Brassica species

Abstract

ABSTRACT Understanding foraging preferences of honey bees (Apis mellifera L.) is essential to maneuver pollinator movement to enhance outcrossing and hence the crop yields. In this communication, we report the role of floral volatile organic compounds (VOCs) in structuring foraging decisions of honey bees. Supercritical fluid extraction of VOCs, coupled with gas chromatography-mass spectrometry, revealed 75 VOCs. Of these, 19 were strong attractants and 8 were strong repellants. Moreover, we detected significant, but variable, species- or genome-level differences in floral scents. Honey bees avoided Brassica juncea cv. PBR357 (0.81 bee visits/sq m/min) and B. carinata cv. PC5 (0.77 bee visits/sq m/min), which possessed peak concentrations of antifeedants or repellents (dibutyl phthalate and 9-octadecenoic acid) in their floral volatiles. B. napus cvs. GSC6 and GSC7 attracted the highest number of bee visitations (1.07 and 0.99 bee visits/sq m/min, respectively), as these possessed VOCs with honey-fruity odor in high amounts and negligible levels of antifeedants. Our results highlight that variability in floral reward chemistry should be considered when breeding crops that are frequently visited upon by bee pollinators to support bee pollinators, in general, and honey industry, in particular.