Multiple approaches to unravel chemical cues used by Diachasmimorpha longicaudata during host searching: behavioral, electrophysiological and gene expression studies

D. F. SEGURA; DEVESCOVI, F.; WULFF, J. P.; C.A. CONTE; S.M. OVRUSKI; M.M. VISCARRET; S.B. LANZAVECCHIA; CLADERA, J.L.

Perugia

Congreso; 6th International Entomophagous Insect Conference; 2019

Diachasmimorphalongicaudata Ashmead (Braconidae) is one of the most commonly used biocontrolagents against Tephritidae fruit flies pests Females parasitize their hostsduring the larval stage, while larvae are still feeding inside the fruit. Tothis end, females use chemical information which is released from the infestedfruit. Our objective is to identify the chemical basis of the attraction of D.longicaudata towards fruit infested by tephritid larvae and address the role oflearning on the use of such information. We found that parasitoid females areable to detect fruit infested with larvae using chemical cues, derived from thehost larvae, as well as from the substrate (rotten fruit) and associatedmicroorganism, like the fungus Penicillum digitatum. We found that females haveinnate preference for specific host fruit odors and the basis of thispreference seems to be related more to the easiness of attacking host larvaeburied into the fruit flesh than to the quality of the host larvae. Color, onthe other hand, did not trigger an innate preference in this species. However,D. longicaudata has the ability to associate visual, as well as chemical, cuesduring host searching, making them more and more efficient at host findingthrough learning. GC-MS analyses of the volatile compounds released by theseattractive sources allowed postulating specific compounds that females woulduse to locate host larvae, which were then tested in electrophysiologicalassays. We also performed a functional analysis of chemoreceptors potentiallyassociated to odor detection in this species. A bioinformatic screening of awhole body transcriptome of D. longicaudata, followed by a phylogeneticanalysis and a tissue expression profile, allowed to postulate fourteen odorantbinding proteins and seven chemosensory proteins. A set of genes were analyzedthrough behavioral and molecular tests in which gene expression was silencedthrough RNAi. Preliminary results showed that several of the selected genes arelinked to the foraging behavior. This approach aimed at connecting behavioral,electrophysiological and gene expression experiments in order to definepotential compounds that could be use in monitoring parasitoid populations aspart of biological control programs.