Male Recombination in a Genetic Sexing Strain of Ceratitis capitata (Diptera: Tephritidae) and Its Effect on Stability

Male recombination was studied between the Y-translocated loci or (orange eye) and wp (white pupae) in a genetic sexing strain of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This strain normally produces wild type males, whereas females are homozygous for the or and wp alleles. In previous mass rearing, another strain with the same translocation was highly unstable. In this study, an overall male recombination frequency of 0.07 and 0.24% was observed between the or gene and the translocation breakpoint (T) and between wp and T, respectively. Only one of the two alleles appeared to be physically linked to the Y chromosome. All aberrant male phenotypes still contained the translocation, indicating that no reversal to the normal karyotype had taken place. A strong positive interference on recombination was observed; a recombinant event between T and wp led in one-third of the cases to a recombinant event also occurring between T and or. Male recombination appeared to be responsible for the initiation of the breakdown of the mass-reared genetic sexing strain, but it could not by itself account for the subsequent rate of breakdown of this strain. The possible role of other factors in accelerating the rate of this breakdown is discussed.