Flowers of European pear release common and uncommon volatiles that can be detected by honey bee pollinators

Abstract

Floral scents are important pollinator attractants, but there is limited knowledge about the importance of single components in plant-pollinator interactions. This especially is true in crop pollination systems. The aim of this study is to identify floral volatiles of several European pear cultivars (Pyrus communis L.), and to determine their potential in eliciting physiological responses in antennae of honey bees (Apis mellifera L.), the most important pollinators of pear. Volatiles were collected by dynamic headspace and analysed by (high resolution) gas chromatography coupled to mass spectrometry (GC/MS) and nuclear magnetic resonance spectroscopy. Antennal responses were investigated by GC coupled to electroantennographic detection (GC/EAD). We trapped in the mean 256 ng of scent per flower and hour (flower −1 h −1) from the different cultivars with either linalool + methyl benzoate or methyl 2-hydroxy-3-methylpentanoate as most abundant compounds. Of the 108 detected pear floral scent components, 17 were electrophysiologically active in honey bee antennae. Among these compounds were (E)-N-(2-methylbutyl)-and (E)-N-(3-methylbutyl)-1-(pyridin-3-yl)methanimine, which were not known from nature before to the best of our knowledge. Most other compounds identified as flower scent in pear are widespread compounds, known from flowers of various other species. Our results provide new insights in the floral volatile chemistry of an important insect-pollinated crop and show for the first time that honey bees have the olfactory ability to detect several pear floral volatiles. These data are an important basis for more detailed studies of the olfactory communication between honey bees and European pear flowers and might in the long term be used to manipulate the attractiveness of pear to obtain optimal fruit set.

Olfactory and Visual Floral Signals of Hedera helix and Heracleum sphondylium Involved in Host Finding by Nectar-Foraging Social Wasps

“…The base of an antenna was connected to the reference capillary, the tip was connected to the recording capillary. The capillaries were connected to silver wires and placed in front of the GC outlet (Lukas et al, 2019).…”

Comparative Analysis of Volatile Compounds in Flowers of Different Actinidia Species

“…These compounds were also attractive to nocturnal bees-major pollinators for cambuci plants (Campomanesia phaea) [30]. In other reports, linalool was observed to attract nocturnal bees Megalopta on guarana (Paullinia cupana) [31], and honey bees on Medicago sativa [32] and pears (Pyrus communis), where (E)-β-ocimene and lilac alcohols were also found to be attractive to bees [33]. Compounds like α-pinene and D-limonene were also found to be attractive to A. mellifera [34], with the second one identified in the A. chinensis' headspace sample.…”

“…29,33, 43,32, 44) -1-yl-2,2-dimethylpropan-1-one (57, 41, 85, 69, 68, 40) 2,2-dimethylcyclopropyl)-2,4-dimethyl-, (Z or E)-(41, 121, 69, 105, 39, 79) were calculated according to van Den Dool and Kratz (1963); ** Retention Indices according to https://webbook.nist.gov/, Van Den Dool and Kratz RI for polar column and, if possible, temperature ramp identical or at least similar to this analysis; *** Mass spectral fragments for unconfirmed compounds in descending order.…”

Floral scents of a deceptive plant are hyperdiverse and under population-specific phenotypic selection

“…2). This difference in the number of scent compounds between A. maculatum and other species cannot just be explained by differences in techniques used for scent analyses, given that scents of a high number of species were analysed using a similar approach as we did (dynamic headspace and thermal desorption of samples) [60][61][62][63][64] . Species closest to the high number of VOCs in A. maculatum include the sapromyiophilous Sauromatum guttatum (Araceae, with altogether 196 different VOCs 65,66 ), as well as the insect-pollinated and rewarding Geonoma macrostachys (Arecaceae, 176 VOCs 60 ) and Echinopsis ancistrophora (Cactaceae, 145 VOCs 67 ).…”

“…Philodendron bipinnatifidum, Araceae 62 ; Pyrus communis, Rosaceae 63 ), but also the sexually deceptive orchid Ophrys sphegodes 68 . Thus, high numbers of compounds are found across a wide range of plant families and are apparently not restricted to a specific pollination system.…”