Breeding for Sucking Insect Resistance

Sucking insect pests are an increasing problem in agriculture, both due to their direct damage and the viruses they transmit. When investigating generally applicable methods for sucking insect resistance we have recently uncovered a natural mechanism for repellence of whiteflies in tomato that is based on the production of specific volatile sesquiterpenes. These components, of which 7-epizingiberene is the most effective, was isolated in a wild tomato accession (Solanum habrochaites) and re-introduced into cultivated greenhouse tomato. 7-epizingiberene is a sesquiterpene with both contact-toxic and repellent properties that is produced and stored in glandular trichomes. We have recently identified the 7-epizingiberene synthase (ShZIS) gene that belongs to a new class of sesquiterpene synthases that exclusively convert the Z-Z,farnesyl-diphosphate (zFPP) precursor molecule in plastids. Expression of the ShZIS gene and known zFPP synthases in the glandular trichomes of cultivated tomato resulted in the production of volatile 7-epizingiberene. These tomato plants thereby gained resistance to whiteflies and several other herbivores that are common pests of tomato and other crops. Production of sesquiterpenes as active insect repellents requires the presence of chemical components that act as precursors. These molecules are present in many crop species. Thereby, the exploitation of this knowledge is feasible in a broad range of agriculturally important crops.