Decoupled Adult and Larval Host Preferences in Tephritid Fruit Flies with a Conserved Oviposition Attractant

Tephritid fruit flies exhibit considerable variability in host range, yet the chemosensory mechanisms underlying adult host selection and larval performance across species with contrasting dietary breadths remain unclear. Here, we investigated behavioral responses of adults and larvae of four species─Bactrocera dorsalis, B. correcta, Zeugodacus tau, and Z. cucurbitae─to seven fruit and vegetable cues. Adult preferences varied, with guava eliciting the strongest attraction in all species. Larval preferences were weaker and decoupled from adult choices. Comparative transcriptomics of guava-exposed antennae identified OBP19d as the most highly upregulated odorant-binding protein across species. RNAi knockdown of BdOBP19d in B. dorsalis reduced electrophysiological responses to guava volatiles and specifically abolished oviposition preference for 4-Ethylacetophenone. Molecular docking, electrophysiology, and behavioral assays collectively validated this interaction. These results reveal a conserved olfactory module for shared host attraction and identify 4-Ethylacetophenone as a candidate attractant for B. dorsalis females, with potential implications for pest management.