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Identification of the Male Determining Factor Reduces the Cost of SIT Application Against Insect Pests

Male Oriental fruit fly, Bactrocera dorsalis. (Photo: A. Rodriguez/IPCL)

The insect family Tephritidae includes many invasive pest species of major agricultural and economic importance and there is an urgent need to develop and apply the sterile insect technique (SIT) against them, as a component of an area-wide integrated pest management approach. A critical step in the SIT applications against insect pests is sex separation. By releasing only male adult insects, the efficiency, efficacy and cost-effectiveness of SIT is greatly increased. Sex separation can be achieved by using genetic sexing strains which allow the elimination of females and the selection and use of males only. In these species, male sex is determined by the Maleness factor, a genetic locus (gene) on the Y chromosome.

The results of a study that has announced the isolation and functional characterization of the male determining factor in three major agricultural pests, the Mediterranean fruit fly (Ceratitis capitata), the Oriental fruit fly (Bactrocera dorsalis) and the olive fruit fly (Bactrocera oleae) were published in the prestigious journal Science on 29 August 2019.

The study, which was carried out by the University of Naples "Federico II", in partnership with the University of Zurich, the University of Perugia, the Hebrew University of Jerusalem, the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture and others, showed that the male determining factor is the Y-linked gene Maleness-on-the-Y (MoY), which produces a small, novel and functionally conserved protein in major Tephritidae fruit fly pest species.

The discovery and characterization of the male determining factor opens the way for the development of novel generic, and potentially more efficient, methods for the construction of genetic sexing strains thus reducing the cost and enhancing the SIT applications against other agricultural pests and also human disease vector species. This will be focus of the new IAEA Coordinated Research Project “Generic approach for the development of genetic sexing strains for SIT applications”.

The SIT has been used for over six decades in many parts of the world against major agricultural tephritid pest species, such as the Mediterranean fruit fly, the Mexican fruit fly Anastrepha ludens, the Oriental fruit fly and the melon fly Zeugodacus cucurbitae. The SIT is based on the use of radiation to sterilize male insects. Through continuous releases in the field, these males are engaged in sterile matings with wild females thus suppressing or even locally eliminating, a target pest population. Every week, more than two billion sterile tephritid males are being released worldwide to manage these major agricultural pests.

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