Entomology Unit
Fruit flies
Genetic Markers for Mediterranean fruit fly SIT Strains
In all fruit fly SIT programmes the released sterile insects are marked with a fluorescent dye to distinguish them from the wild insects. This procedure is not always accurate and can lead to a misclassification of captured flies. Two different types of markers have been tested for their usefulness for the identification of genetic sexing strains.
1) A specific mitochondrial haplotype can be used to unequivocally distinguish released from wild insects. The marker is PCR-based and provides a rapid assay. The marker can be very useful if there is a dispute concerning a possible accidental release of fertile insects from a facility. The mitochondrial marker was very useful to interpret trap catch data for the medfly programme in South Africa.
2) The genetic marker Sergeant (Sr2) has been introduced into genetic sexing strains. It is visible as three white stripes on the abdomen as compared to the two stripes in a wild type fly. The mutation is dominant and in the sexing strain, only the males are marked with this mutation. Several tests have shown that Sr2 has no negative affect on mating or productivity. Furthermore the mutation is easy to monitor and has a very good penetrance.