ARS | Publication request: In Situ Volatile Collection, Analysis, and Comparison of Three Centaurea Species and Their Relation to Biocontrol with Herbivorous Insects

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 9, 2008
Publication Date: March 25, 2008
Citation: Beck, J.J., Smith, L., Merrill, G.B. 2008. In Situ Volatile Collection, Analysis, and Comparison of Three Centaurea Species and Their Relation to Biocontrol with Herbivorous Insects. Journal of Agriculture and Food Chemistry.56(8):2759-2764.

Interpretive Summary: Yellow starthistle (Centaurea solstitialis L. Asteraceae), YST, is an invasive plant listed as a noxious weed in several western states of North America and is the target of classical biological control, which involves release of herbivores known to be specific to this plant. These insects often choose their host plant based on the volatile organic compounds (VOCs) emitted by the plant, either ambient and/or after naturally occurring damage. Accordingly, volatile analysis of host plants can provide insight into VOCs that offer behavioral cues that either attract and/or repel the insect. To aid in this endeavor, a customized collection bag was utilized to perform in situ volatile collection by means of solid-phase microextraction. Volatile identification was performed by gas chromatography coupled to a mass selective detector and the VOC differences between YST, C. cyanus (bachelor’s button), and C. cineraria (dusty miller) were determined. The plants YST and bachelor’s button have been reported to attract the adult female weevil, Ceratapion basicorne Illiger (Coleoptera: Apionidae), a candidate for biological control, whereas dusty miller does not attract the weevil. Herein, we report major differences of volatile output of leaves with varying levels of mechanical damage to each of the three species: intact (control), punctured, cut, and mangled. Major VOCs unique to dusty miller include the sesquiterpenes cyclosativene, alpha-ylangene, and trans-alpha-bergamotene. The compound trans-beta-farnesene was unique to YST and bachelor’s button.

Technical Abstract: Centaurea solstitialis, commonly known as yellow starthistle, is an invasive plant listed as a noxious weed in the western areas of North America and is the target of classical biological control, which involves release of herbivores known to be specific to this plant. These insects often choose their host plant based on the volatile organic compounds (VOCs) emitted. Accordingly, volatile analysis of host plants can provide insight into VOCs that may attract and/or repel the insect. To this end, solid-phase microextraction (SPME) and a customized collection bag were utilized to perform in situ volatile collection on intact and mechanically damaged leaves of C. solstitialis, C. cyanus, and C. cineraria. Volatile identification was performed by GC-MS and the VOC differences were determined. The plants C. solstitialis and C. cyanus have been reported to attract the weevil, Ceratapion basicorne, a candidate for biological control, whereas C. cineraria does not attract the weevil. Major VOCs unique to C. cineraria include the sesquiterpenes cyclosativene, alpha-ylangene, and trans-alpha-bergamotene. The compound trans-beta-farnesene was unique to C. solstitialis and C. cyanus.