Silencing RpadOrco disrupts host seeking, semiochemical avoidance and reproductive fitness in Rhopalosiphum padi

BACKGROUND The odorant receptor co‐receptor (Orco) is an important component of the insect olfactory system. However, the biological functions of Orco in the bird cherry‐oat aphid, Rhopalosiphum padi , remain unclear, particularly its roles in olfactory perception, host‐plant selection and aphid fitness. RESULTS RpadOrco was predominantly expressed in the antennae. RNA interference‐mediated knockdown of RpadOrco significantly reduced electroantennogram responses to 11 behaviorally relevant odorants, including plant volatiles, the repellent methyl salicylate (MeSA) and the alarm pheromone (E)‐ β ‐farnesene (EBF). In Y‐tube olfactometer assays, RpadOrco ‐silenced aphids no longer showed significant orientation toward wheat and exhibited attenuated avoidance responses to MeSA and EBF. Silencing RpadOrco also increased the proportion of aphids that made no choice in the Y‐tube olfactometer assays and significantly reduced body weight and fecundity in the F 0 generation, without affecting survival. However, no significant changes were detected in developmental duration, longevity or life‐table parameters in the F 1 generation. CONCLUSION RpadOrco plays an important role in host‐plant orientation, semiochemical perception and reproductive fitness in R. padi . Its simultaneous effects on olfactory behavior and fecundity identify RpadOrco as a potential molecular target for developing behavior‐disrupting and RNAi‐based approaches to cereal aphid management.