TLC-based bioassay to isolate kairomones from tea tree essential oil that attract male Mediterranean fruit flies, Ceratitis capitata (Wiedemann)

Authors: Tabanca, Nurhayat; NIOGRET, JEROME - Niogret Ecology Consulting; Kendra, Paul; EPSKY, NANCY - Retired ARS Employee

Submitted to: Biomolecules EISSN 2218-273X
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2020
Publication Date: 4/28/2020
Citation: Tabanca, N., Niogret, J., Kendra, P.E., Epsky, N.D. 2020. TLC-based bioassay to isolate kairomones from tea tree essential oil that attract male Mediterranean fruit flies, Ceratitis capitata (Wiedemann). Biomolecules EISSN 2218-273X. 10(5): 683. https://doi.org/10.3390/biom10050683.
DOI: https://doi.org/10.3390/biom10050683

Interpretive Summary: The Mediterranean fruit fly or medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the world’s most destructive agricultural pests. New attractants could improve detection, suppression and eradication measures of this pest. In our previous study, we found that tea tree oil (TTO) is a highly attractive short-range attraction of sterile male medflies. To identify the kairomones responsible for this activity, scientists at SHRS developed a method in a combination of thin-layer chromatography (TLC) with attraction bioassays. After TLC development, the TLC chromatogram was divided into five zones based on TTO profile and the plate exposed to the flies where they aggregated around kairomones directly on the TLC surface. The highest attraction was observed in bioassays of zones 1 and 3. Additionally, TTO was fractionated by preparative TLC, yielding five fractions for electroantennography (EAG) analysis to quantify antennal olfactory responses of fractions. In laboratory bioassays and electroantennographic analyses, zone 1 and fraction 1 were found to elicit strong attraction and zone 3 and fraction 3 were found to be the next higher attractants for C. capitata. In conclusion, the TLC-based bioassay can be an effective and rapid screening method for the identification of insect kairomones from complex mixtures such as essential oils.

Technical Abstract: The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) poses a major threat to fruit and vegetable production in the United States and throughout the world. New attractants and detection methods could improve control strategies for this invasive pest. In this study, we developed a method that combined thin-layer chromatography (TLC) of tea tree essential oil (TTO) (Melaleuca alternifolia) with short-range bioassays to isolate attractive kairomones for male C. capitata. After development, the TLC chromatogram indicated that TTO separated into five major spots, designated as zones 1 to 5. When the TLC plate was exposed to flies, zones 1 and 3 were strongly attractive to male C. capitata. To confirm activity, the developed TLC plate was cut into five zones which were then tested in short-range bioassays. Again, flies were observed to aggregate around zones 1 and 3, which corresponded with Rf values of 0.93 and 0.59. In addition, zones 1 to 5 were separated using preparative-TLC, and olfactory responses to volatile emissions from the five fractions were quantified by electroantennography (EAG). Highest amplitude EAG responses were recorded with fractions 1 and 3, further supporting the bioactivity of these samples. In conclusion, a TLC-based bioassay system can provide an eective, rapid screening protocol for initial isolation of insect kairomones from complex mixtures such as essential oils or plant extracts. Further analysis of TTO fractions 1 and 3 is needed to identify the specific constituents attractive to male C. capitata.