2018 ASHS Annual Conference

Piercing-sucking insects such as aphids pose a serious problem in the commercial production of horticultural crops including tomato, since damage is caused not only by direct feeding, but also by transmission of viruses for which these herbivores serve as vectors. Current control strategies involving synthetic insecticides are increasingly considered as problematic due to emerging resistances, costs for growers, and concerns of consumers, highlighting the need to develop new efficient and sustainable approaches to control these pests. Recent studies of terpene production in glandular trichomes of tomato plants, found on their leaves and stems, and known to be involved in plant-insect interactions, demonstrated significant differences between cultivated and wild tomato species, as well as quantitative and qualitative variation among wild tomato accessions. Since these wild tomato accessions potentially represent good sources of defensive traits against aphids, we have performed a number of assays to compare the performance and feeding behavior of the potato aphid, Macrosiphum euphorbiae, on leaves of cultivated tomato (Solanum lycopersicum) and multiple wild tomato accessions (Solanum habrochaites) representing different terpene chemotypes. Non-choice assays demonstrated that longevity and fecundity of potato aphids was significantly lower on two groups of S. habrochaites accessions compared to S. lycopersicum. Subsequently, we analyzed aphid feeding on an artificial medium containing either leaf extracts with glandular trichome derived terpenes from cultivated and wild tomato accessions, or pure terpene compounds. Our analysis of aphid survival, as well as accumulation of salivary sheath and honeydew production, both indicators of aphid feeding, suggest that selected glandular trichome derived terpenes found in some S. habrochaites accessions influence aphid performance by affecting their feeding behavior. In addition we performed olfactometer choice assays to study the effect of terpenes emitted from different tomato accessions on the search behavior of winged potato aphids towards host plants. The same S. habrochaites accessions that showed significant effects in the previous non-choice and feeding assays, were also found to be repellent towards winged aphids. Moreover, addition of leaf extracts of these S. habrochaites accessions or respective pure terpene compounds to leaves of cultivated tomato plants significantly reduced the attractiveness of these to aphids. The identification of several terpenes from S. habrochaites accessions with the potential to affect the overall performance, feeding and search behavior of potato aphids no allows us to introduce these defensive traits into cultivated tomato by introgression and metabolic engineering.