Genetic transformation of the olive fruit fly

The Olive Fruit Fly, Bactrocera oleae is the major pest of commercial olive production worldwide. Larvae causes crop losses of ~30% in Greece and Italy. Current control relies on heavy insecticide use. Several other fruit flies are effectively controlled by use of the Sterile Insect Technique (SIT)1-3; this project proposes to develop genetic methods to overcome some of the key limitations to the use of SIT against Olive fly. SIT is an environmentally friendly, species-specific method of pest control. It depends on the mass rearing, sterilisation and release of large numbers of the sterile males who mate with wild females, causing a reduction in the wild population in the subsequent generation. If enough sterile males are released for a sufficient time, the target population will collapse. SIT relies on irradiation to sterilise the target pest species but this can have a negative impact on the released insects. This and other problems associated with current SIT programs could be overcome by the use of recombinant DNA methods. Oxitec Ltd is the world leader in developing such approaches. Though SIT has been extremely successful against other tephritid fruit flies, there are specific difficulties for SIT against Olive fly. One problem is that lab-reared insects have altered diurnal rhythms, so they prefer to mate earlier in the day than their wild counterparts. This would tend to lead to the sterile insects preferentially mate each other and failing to mate with the wild insects. Male-only release would overcome this problem, as the males will look for receptive females until they find them, and would also eliminate a second problem of sterile stings. Development of a genetic sexing mechanism, whereby females can be removed to give a male-only population for release, is therefore the highest priority for Olive fly SIT, and the primary goal of this project. Oxitec's core proprietary technology, known as RIDL, first demonstrated in Drosophila4 and now being applied to real pest insects5,6, provides a viable means of overcoming the limiting constraints of Olive fly SIT. The aim of the proposed project is to develop RIDL strains of Olive fly that replace the need for sterilisation by irradiation and also act as a genetic sexing mechanism7. There are three specific objectives within the project: (1) development of a non-sex specific dominant repressible lethal, functional in Olive fly which replaces the need for irradiation (2) an sex-specific repressible dominant lethal, which would also act as a genetic sexing mechanism and (3) an early acting, sex-specific repressible dominant lethal, which would act as a genetic sexing mechanism, irradiation replacement and avoid any fruit damage. The proposed research will benefit from the unique expertise within Oxitec of generation of RIDL strains of other pest species, especially Medfly and Mexfly, as well as the extensive experience of Drosophila molecular genetics and transformation in both the academic and company laboratories. Genetic engineering of insect pests is in its infancy and there is much cutting-edge research to be done as we progress towards the applied objectives described above. Our experience with other insects enables us to address these issues and develop a novel, sustainable, low-environmental-impact pest control strategy for a pest of great economic importance. References 1. Knipling, E. J. Econ. Entomol. 48, 459-62 (1955). 2. Krafsur, E. J. Agric. Entomol. 15, 303-17 (1998). 3. Robinson, A. Mutation Research 511, 113-32 (2002). 4. Thomas, D. T., et al. Science 287, 2474-6 (2000). 5. Gong, P., et al. Nat. Biotech. 23, 453-6 (2005). 6. Fu et al. Nat. Biotech. 25, 353-7 (2007).