The secondary metabolism of plants plays a key role in plant-insect interactions. Among the various classes of metabolites produced, volatile organic compounds (VOCs) play important echophysiological roles, including the attraction of pollinators. This work aimed to develop a method to extract VOCs using headspace (HS) and solid-phase microextraction (SPME), which can be applied in future studies to contribute to the understanding of the role of VOCs in the pollination process. Therefore, a HS-SPME method combined with gas chromatography-mass spectrometry (GC-MS) was developed for the extraction and characterization of VOCs of melon flowers (Cucumis melo L.). The extraction was carried out with the fibers PDMS, DVB/ CAR/PDMS and CAR/PDMS for the times 15, 30, and 45 min. Fifty compounds belonging to the following chemical classes were identified: terpenes, hydrocarbons, esters, ethers, ketones, aldehydes, and alcohols. CAR/PDMS fiber extracted the largest amount of compounds, and was more efficient for the extraction of volatile compounds with lower molecular weight, low boiling point and ideal for analytes in low concentration. Therefore, the evaluated method proved to be a promising tool for the analysis of VOCs of melon flowers, to be applied in new studies of the relationships between chemical composition and the processes of attraction of pollinators.

Pollination is essential for food production in the world, but in pollinator-dependent crops it relies on the attraction of pollinators to flowers. However, crop varieties vary in their attractiveness to flower visitors and volatile compounds emitted by flowers may play a significant role in attracting or repelling pollinators. Here, we investigated the volatile organic compounds (VOCs) present in both male and hermaphrodite flowers of five commercial types of melon Cucumis melo (Cantaloupe, Charentais, Galia, Piel de sapo and Yellow), and their role in attracting or repelling Apis mellifera foragers. We found significant variation in the identity and proportion of these chemical compounds produced by both melon types and flower genders and observed significant positive and negative correlations between the amount of D-Limonene and Benzaldehyde (bee attractants) and α-Pinene (bee repellent), respectively, to the number of bee visits to flowers particularly in the Cantaloupe type and hermaphrodite flowers, the most visited ones. Our results suggest that differences in the composition of melon floral VOCs and the proportion of the different compounds play significant role in the number of visits by A. mellifera with possible implications to pollination and fruit yield. It also implies to the perspective of breeding varieties more attractive to pollinators through the selection of flower lines richer in bee-attractant and/or poorer in bee-repellent volatiles.

Melon is a pollinator-dependent crop that relies mainly on bees to set fruits. However, manselected varieties vary in their attractiveness to flower visitors, and some flower genders and melon types may be less visited than others, harming pollination. We investigated the nectar composition of male, female and hermaphrodite flowers of 270 individuals of five commercial melons Cucumis melo (Cantaloupe, Charentais, Galia, Piel de Sapo, and Yellow), and its role in flower visit by Apis mellifera foragers. We found that melon nectar is composed mainly of sugars and amino acids such as tyrosine, phenylalanine, tryptophan, and flavonoids kaempferol3-O-neohesperidoside, luteolin hexoside, and kaempferol rhamnoside. But the amount of these chemical compounds varies among the flower genders. We also developed an accurate regression model to predict the number of bee visits to melon flowers based on the nectar composition. Our results indicate that nectar composition plays little role in bee discrimination among flowers of different melon types but is essential to the honeybee choice between flower gender. The amounts of phenylalanine (49.40%) and tryptophan (12.05%) in the nectar are related to bee preference for hermaphrodite flowers. More visits to hermaphrodite flowers contribute to setting and developing well-formed fruits, increasing productivity.

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