Summary
Eggplant (Solanum melongena) suffers severe losses due to a multi-insecticide resistant lepidopteran pest, shoot and fruit borer (SFB, Leucinodes orbonalis). Heavy and combinatorial application of pesticides for SFB control renders eggplant risky for human consumption.
We observed that 1) ovipositing SFB females can find even solitary plants of susceptible varieties and 2) they do not oviposit on Himalayan eggplant variety RC-RL-22 (RL22). We hypothesized that the olfactory cues influence ovipositing female’s host choice.
To find these cues, leaf volatile blends of seven eggplant varieties were profiled using GCMS. Seven compounds were present in >2.5-fold concentrations in RL22 than the other varieties. In choice assays, oviposition deterrence efficacies of these candidate compounds were independently tested by their foliar application on SFB-susceptible varieties. Complementation of geraniol, which was exclusively found in RL22, reduced oviposition (>90%). To validate geraniol’s role in RL22’s SFB-deterrence, we silenced RL22’s geraniol synthase gene using virus-induced gene silencing. Geraniol biosynthesis suppression rendered RL22 SFB-susceptible; foliar geraniol application on the geraniol synthase-silenced plants restored oviposition deterrence.
We infer that geraniol is RL22’s SFB oviposition deterrent. The use of natural compounds like geraniol, which influence the chemical ecology of oviposition can reduce the load of hazardous larvicidal pesticides.
Competing Interest Statement
The authors have declared no competing interest.
