Alkyl-Substituted δ-Lactones Derived from Dihydrojasmone and Their Stereoselective Fungi-Mediated Conversion: Production of New Antifeedant Agents

Antifeedant Potential of Geranylacetone and Nerylacetone and Their Epoxy-Derivatives against Myzus persicae (Sulz.)

Geranylacetone and nerylacetone are natural sesquiterpenoids, which play various roles in plant-insect interactions, including the deterrent and repellent effects on herbivores. The structural modifications of natural compounds often change their biological activities. The aim of the study was to evaluate the effect of geranylacetone, nerylacetone and their epoxy-derivatives on the probing and settling behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae). The no-choice test using the Electrical Penetration Graph (EPG) technique showed that the probes before the first phloem phase were usually shorter than 3 min, which means that they were terminated within the epidermis and/or outer layers of mesophyll. This resulted in a tendency to delay the initiation of the phloem phase in aphids, which reflects a weak preingestive deterrent activity of the studied compounds at the level of non-vascular tissues. Most M. persicae showed bouts of sustained phloem sap ingestion. However, the 24-h free-choice test demonstrated that aphids did not settle on the leaves treated with geranylacetone, nerylacetone, and their epoxy-derivatives. The refusal to settle after the consumption of phloem sap on treated plants indicated that the studied compounds had postingestive deterrent activity. The epoxidation of geranylacetone and nerylacetone did not evoke significant changes in their activity profiles.

Novel Hydroxy- and Epoxy-cis-Jasmone and Dihydrojasmone Derivatives Affect the Foraging Activity of the Peach Potato Aphid Myzus persicae (Sulzer) (Homoptera: Aphididae)

Jasmonates show great potential in sustainable agriculture due to their various roles in natural mechanisms of plant defense, and because they are non-toxic, non-mutagenic, and easily metabolized. The aim of the study was to explore structure⁻activity relationships of dihydrojasmone, cis-jasmone, and their derivatives at the plant⁻aphid interface. We focused on the behavioral responses of aphids, following the exogenous application of natural jasmonates and their derivatives to the host plants. Aphid probing behavior was examined using an electrical penetration graph technique (EPG). The chemoenzymatic transformation of cis-jasmone and the activity of two new derivatives are described. The application of cis-jasmone, dihydrojasmone, the hydroxyderivatives, epoxyderivatives, and alkyl-substituted δ-lactones hindered the foraging activity of Myzus persicae (Sulz.) (Hemiptera: Aphididae) during early stages of probing at the level of non-phloem tissues. The application of saturated bicyclic epoxy-δ-lactone enhanced plant acceptance by M. persicae. Jasmonate derivatives containing a hydroxy group, especially in correlation with a lactone ring, were more active than natural compounds and other derivatives studied. Jasmonates of the present study are worth considering as elements of sustainable aphid control as components of the "push⁻pull" strategy.