Domestication of Ugni molinae reduced predator-attracting compounds

Study compared volatile compounds of wild and domesticated ecotypes of the species Ugni molinae, a shrub native to southern Chile, observing how it influences the behavior of insect pests and natural predators. The conclusion: the plant lost part of its natural chemical defenses in the process of domestication.

Researchers from the University of La Frontera and the CGNA center analyzed seven ecotypes: three wild and four domesticated, all cultivated under the same conditions.

The team used olfactory traps and chromatographic analysis to measure the emission of volatile organic compounds (VOCs). The results confirmed that wild plants emit significantly more VOCs than their domesticated counterparts.

These compounds act as chemical signals. Some attract pest predators, such as larvae of Chrysoperla defreitasi. Others repel herbivores like Myzus persicae.

Among the compounds most emitted by wild plants are 2-hexanone, 1,8-cineole and alpha-caryophyllene — all absent or in low concentration in cultivated ecotypes.

In the olfactometric test, lacewing larvae preferred volatile extracts from wild plants. The olfactory preference index (OPI) for the W1 ecotype (ancestral) reached 1,64. In domesticated species, such as D1, the OPI was close to 1, indicating a lack of attraction. Aphids showed the opposite behavior: they were more attracted to compounds from domesticated ecotypes.

This inversion has direct consequences for agricultural management. By losing substances that attract natural predators, the plant becomes more susceptible to the action of pests. The ecological cycle of indirect protection is broken.

The study also evaluated isolated compounds. alpha-Caryophyllene and 2,4-dimethyl-acetophenone showed greater attractiveness to lacewings. 2-hexanone and 3-hexanol favored the choice of aphids. The predators' preference increased with the concentration of the compounds — up to 100 ppm. That of aphids did not. This behavior reinforces the selective role of VOCs in communication between plants and insects.

The domestication of U. molinae prioritized productivity and fruit size. These characteristics were achieved, but at the expense of defensive chemical diversity. The study confirms the hypothesis of reduced defense due to domestication, already verified in species such as tomato, corn and cotton.

The research highlights the importance of incorporating ecological characteristics into breeding programs. Maintaining or reintroducing defensive compounds can reduce dependence on chemical inputs. Strategies such as crossbreeding with ancestral ecotypes, using plant consortia or microbiological inoculants are possible paths.

More information at doi.org/10.3390/insects16060594