SummaryEggplant (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.

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 gravid SFB females do not oviposit on Himalayan eggplant variety RC‐RL‐22 (RL22). We hypothesized that RL22 contained an antixenosis factor. Females' behavior indicated that the RL22 cue they perceived was olfactory. To identify it, leaf volatile blends of seven eggplant varieties were profiled using solid phase microextraction and gas chromatography mass spectrometry. Seven RL22‐specific compounds were detected in the plant headspace. 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 characterized RL22's geraniol synthase and silenced its gene in planta, 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 synthetic larvicides.

Forest slashing and burning is a key characteristic of shifting cultivation. Its intensification is a major anthropogenic cause of deforestation, as it reduces forest resilience. We analyzed the reforestation process in the regenerating shifting cultivation lands in India's Western Ghats, a megadiversity hotspot. An actinorhizal shrub, Elaeagnus conferta, was associated with the regenerating thickets' higher density and higher species diversity. Its presence increased the thicket density by >2.8-fold and the species diversity by >2.5-fold; these thickets showed >1.5-fold higher Shannon's diversity index than those without it. Moreover, the thickets containing E. conferta showed >7-fold more multi-species seedlings. Liquid chromatography-mass spectrometry analysis showed that rhizosphere soils of E. conferta containing thickets had >10-fold higher gibberellic acid (GA 3 ) concentrations than the E. conferta-deplete thickets. When E. conferta was potted separately, its root nodules, roots, and rhizosphere soil showed about 3.6, 2.0, and 0.4 μg/g GA 3 , respectively. These E. conferta root and rhizosphere soil GA 3 concentrations were >10-fold higher than those shown by other co-occurring species. These elevated GA 3 levels were likely due to E. conferta's association with the rhizosymbiont Frankia elaeagni. Frankia elaeagni's GA 3 synthesis may promote plant recruitment by stimulating seed germination and explain why we measured higher seedling density and plant diversity in E. conferta containing thickets. We hypothesize that E. conferta plays a two-stage pioneering role in the reforestation process by providing GA 3 to facilitate seed germination and providing nitrogen for the developing plantlets. We recommend the inclusion of E. conferta in Western Ghats' reforestation programs.