| Abstract |
The olive fruit fly Bactrocera oleae (Dacus) is the most destructive pest of olives worldwide. There is increasing interest in biological methods for control of this species, in part because of worldwide awareness to the harmful effects of insecticides and other factors such as increasing insect resistance to existing insecticides. The Sterile Insect Technique (SIT) provides a new biological method for dealing with pests, with great application success in various parts of the world. It involves rearing large numbers of insects that are then sterilized before field release. Although equal numbers of the two sexes are initially produced, females are separated and discarded before release because are considered detrimental to control efforts. If sufficient numbers of competitive sterile males are released, the majority of the wild females in the field will mate with them and thus will not produce viable offspring.
In this thesis, we have demonstrated stable and efficient transposase-mediated germ-line transformation of this insect with a Minos based EGFP expressing vector (Koukidou et al., 2006). Using Minos based transformation, we then started to develop a genetically engineered strain for SIT application, employing the sex determining gene transformer 2 (tra2). The tra2 gene is one of the regulatory genes that control sex determination in Drosophila melanogaster. The wild type function of tra2 has been shown to be required for female specific splicing of the doublesex gene as well as for normal spermatogenesis in male Drosophila. The sex determining role of B. oleae tra2 gene (Botra2) was assayed by RNA interference (RNAi) in the second part of the thesis. Injection of B. oleae pre-blastoderm embryos with increasing concentrations of Botra2 dsRNA resulted in an increased number of male flies and a corresponding decrease of XY male fertility, confirming the gene’s functional conservation to its Drosophila orthologue. Based on our RNAi results, as the third part of this thesis, we have developed a Minos based EGFP expressing plasmid, where tra2 expression is repressible. Introduction of this transposon into the germline of B. oleae should result in a strain that, when tra2 expression is induced, will give sterile, male-only progeny, useful for SIT applications.
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Ανάπτυξη και χρήση μεθόδων γενετικής μηχανικής για εφαρμογή στην καταπολέμηση του δάκου της ελιάς
