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Cardiff University (2015)

Development of genetic control technology for Tephritid pests

Asadi, Romisa

Titre : Development of genetic control technology for Tephritid pests

Auteur : Asadi, Romisa

Université de soutenance : Cardiff University

Grade : Doctor of Philosophy (PhD) 2015

Résumé
The olive fly, Bactrocera oleae, is the single most important pest in olive plantations. Currently, control of olive fly relies on the heavy use of chemical pesticides. The sterile insect technique (SIT) is a highly effective, species-specific and environmentally non-polluting method of pest control that involves the mass-release of sterilised insects. SIT is considered a potentially valuable method for the control of olive fly. Previous olive fly SIT attempts failed due to an inability to produce large numbers of flies, low egg production rates and lack of a method to separate the sexes. RIDL (Release of Insects carrying a Dominant Lethal) is a biotechnology-based variant of SIT. This could potentially overcome several problems of classical SIT, including the radiation damage to insects. To develop fly male sterility, we have identified and tested several different germline specific promoters and several potential effector genes. These have been linked to the ‘tet-off’ expression system, which is suppressed by dietary tetracycline, and were initially tested in the Mediterranean fruit fly (Ceratitis capitata) for practicality. In the absence of tetracycline, tTAV binds to its target sequence, tetO, and activates expression of downstream genes. Flies carrying a promoter construct (topi-tTAV or β2-tubulin-tTAV) in medfly were crossed to flies carrying effector constructs (tetO-I-ppoI, tetO-3zincfinger or tetO-ProtamineFokI). A combination of β2-tubulin-tTAV and tetO-ProtamineFokI gave the best male sterility in medfly. A construct containing both elements was designed, and transposon-based germline transformation was used to generate and test ten olive fly strains. Progeny assessment off tetracycline indicates high penetrance of the male-sterile phenotype in all strains, with only 0.0-2.4% viable progeny ; this sterile phenotype appears to be completely suppressed by provision of dietary tetracycline.

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