Elevated CO2-mediated plant VOCs change aggravates invasive thrips occurrence by altering their host-selection behaviour

Globally rising atmosphere CO₂ has been predicted to affect the emission of plant volatile organic compounds (VOCs) and the interaction with insect herbivores. CO₂-mediated plant VOCs change might contribute to develop effective management strategies for insect pests by using VOCs related biological control methods. In this study, we analysed the effect of elevated CO₂ on the host-selection behaviour of western flower thrips (Frankliniella occidentalis) and studied how they were affected by the release of VOCs from kidney bean plants (Phaseolus vulgaris). A four-chamber olfactometer was used to quantify the host-selection of F. occidentalis for P. vulgaris. Elevated CO₂ increased F. occidentalis' selection for P. vulgaris wounded by mechanical damage (MD) and thrips infestation (TI) that might via regulating the gene expression of CSP1, CSP1-q, OBP1 and OBP1-q in F. occidentalis. Besides, we cultivated kidney beans at ambient CO₂ (400 ppm) and elevated CO₂ (800 ppm), and quantified the emission of plant VOCs by using GC-MS. Thirty VOCs belonging to ten chemical groups were identified from P. vulgaris, including aromatic hydrocarbons, ethers, alkanes, cycloalkanes, alcohols, alkenes, aromatic derivatives, phenols, ketones and esters. Furthermore, six VOCs from P. vulgaris were significantly affected by CO₂ level, wounding way and the interaction between them, including ethyl benzene, 1,3-dimethyl benzene, 1,3-dimethyl-4-ethyl benzene, (E,E,E,E)-squalene, 2,6-ditert-butyl-4-methyl phenol and dioctyl phthalate. Our study indicates that elevated CO₂ might increase the host-selection of F. occidentalis for wounded P. vulgaris due to the changed plant VOCs.