Bees choose melon flowers by smell

Producers had already observed that melon flowers are unattractive to bees, compared to the vegetation that borders the plantations. Now scientists have discovered that the honey bee (Apis mellifera) distinguishes between flowers of different types of melon. Furthermore: they prefer not to visit the flowers of some of them, which is a problem for commercial plantations, as the melon tree is highly dependent on bee pollination to produce fruit.

The answer to this behavior lies in the variation in volatile compounds exhaled by flowers. Each type of melon has a different bouquet, including attractive or repellent compounds. The presence of the volatile related to repellency is decisive in the behavior of bees, even when there are attractive compounds.

Researchers from Embrapa Agroindústria Tropical (CE) and the Federal University of Ceará (UFC) studied the behavior of bees in the flowers of the five main types of melon cultivated in Brazil: Amarelo, Cantaloupe, Charentais, Gália and Pele de Sapo. Scientists linked the visits to the volatile compounds emanated. They observed positive correlations between the number of visits and the amount of D-Limonene and Benzaldehyde and negative correlations with α-Pinene.

“The most common volatile compound in the melon flower is correlated with not visiting”, says Embrapa researcher Fernando Aragão, who is developing work on the genetic improvement of melons and has been studying, in partnership with UFC, pollination in melons for nine years. culture.

Researcher Guilherme Zocolo, who worked on the identification of volatile compounds at Embrapa's Multi-User Natural Products Chemistry Laboratory, explains that the presence of a repellent compound in melon flowers may seem strange, but the substance works to protect plants from insects phytophagous, flower and leaf eaters. “It’s the plant’s defense to ward off insect pests,” he explains.

The experiment

In commercial plantations, a single type of melon tree occupies large areas, so it is difficult to associate variations in bee behavior with different types of melon. To carry out the study, forty plots were installed, with eight replications of each type of melon tree, in the same area, for two consecutive years.

The researchers monitored all bee foraging. They also collected data on the characteristics of the flower, nectar, pollen and exhaled volatile compounds. They cross-referenced all the information to observe the factors that influenced visitation and evaluated the effects on fruit production and quality.

Professor Breno Freitas, coordinator of the UFC Bee Research Group, says that during the studies, the researchers realized that the cantaloupe melon, which was significantly more visited than the others, only had one repellent compound and in small quantities, α -Pinene, and various attractive compounds. Yellow melon has some attractive compounds, but in a smaller quantity than cantaloupe, and only has a repellent, but in a much larger quantity. “Charentais is attractive in small quantities and the rest is repellent, some in large quantities. This explains why the bee visits the flowers of this type of melon tree less.”

Bee is responsible for 80% of production

“It has been demonstrated that it is necessary to carry out pollination management adjusted for each type of melon tree”, concludes Freitas. For the professor, the study is important because pollination with Apis mellifera is responsible for 80% of melon production. “Melon producers use bee colonies in the area because, without them, they cannot even cover production costs,” he reveals.

In addition to assisting in the management of bees in crop pollination, the results of the study will be useful for melon genetic improvement programs. “With genetic improvement, it is possible to increase the concentration of components that attract bees, so that they visit more melon flowers,” says Aragão.

The idea, according to him, is to start identifying genotypes that have a higher concentration of the most attractive components or a lower concentration of less attractive or repellent compounds. “Through molecular biology, with markers, we will be able to identify genes that are associated with the production of interesting compounds and begin working towards fixing these genes in new populations”, he adds.

Aragão points out that the majority of crops currently cultivated are the product of plant genetic improvement programs, carried out to select desired characteristics, but, in general, there was no concern with floral characteristics related to attracting pollinators. Based on the results of the study, another possibility is to produce a commercial formulation using the molecules involved in attracting bees to assist in the pollination process.

Freitas highlights that improving pollination efficiency is a way to increase agricultural productivity, that is, increasing production in the area already cultivated without the need to expand cultivation to new areas. “It is one of the ways to meet the increase in population and the need to produce food with less environmental impact”, he declares.