Abstract
Among Australian endemic tephritid fruit flies, the sibling species Bactrocera tryoni and Bactrocera neohumeralis have been serious horticultural pests since the introduction of horticulture in the nineteenth century. More recently, Bactrocera jarvisi has also been declared a pest in northern Australia. After several decades of genetic research there is now a range of classical and molecular genetic tools that can be used to develop improved Sterile Insect Technique (SIT) strains for control of these pests. Four-way crossing strategies have the potential to overcome the problem of inbreeding in mass-reared strains of B. tryoni. The ability to produce hybrids between B. tryoni and the other two species in the laboratory has proved useful for the development of genetically marked strains. The identification of Y-chromosome markers in B. jarvisi means that male and female embryos can be distinguished in any strain that carries a B. jarvisi Y chromosome. This has enabled the study of homologues of the sex-determination genes during development of B jarvisi and B. tryoni, which is necessary for the generation of genetic-sexing strains. Germ-line transformation has been established and a draft genome sequence for B. tryoni released. Transcriptomes from various species, tissues and developmental stages, to aid in identification of manipulation targets for improving SIT, have been assembled and are in the pipeline. Broad analyses of the microbiome have revealed a metagenome that is highly variable within and across species and defined by the environment. More specific analyses detected Wolbachia at low prevalence in the tropics but absent in temperate regions, suggesting a possible role for this endosymbiont in future control strategies.
Highlights
The family Tephritidae includes some of the most significant pests of horticulture in the world
The results demonstrated that the C. capitata b2-tubulin promoter works successfully in the genus Bactrocera
A range of genetic tools is available for B. tryoni that will inform the development of improved Sterile Insect Technique (SIT) strains
Summary
The family Tephritidae includes some of the most significant pests of horticulture in the world. The broad applicability of the piggyBac-based vector systems and the variety of cleverly designed constructs that have been shown to be functional in tephritid pest species [79] mean that the development of TSS strains for B. tryoni, using transgene constructs designed around the highly conserved sex-determination genes, tra and tra-2, is feasible in the near future. A male-only Wolbachia infected fly line may be released for population control, and this was first field tested as incompatible insect technique (IIT) for naturally infected Rhagoletis cerasi (reviewed in [121]), as an alternative to radiation-based SIT. It is likely that frequent ecological interactions of tropical Australian fruit flies (e.g. in shared host fruits or through parasitoid wasps) results in frequent exposure of tephritid species to Wolbachia resulting in horizontal Wolbachia transmission [126]
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