Improved stability of genetic sex-separation strains for the Mediterranean fruit fly, Ceratitis capitata

Abstract

In the existing genetic sexing strains for the medfly, Ceratitis capitata, male recombination leads to breakdown of the sexing mechanism under mass rearing conditions. The rate of breakdown depends on the recombination frequency and on the fitness of the recombinants. We have tested two different sexing genes, white pupa and a temperature sensitive lethal, in combination with the translocation T(Y;5)30C. Both sexing strains broke down, although at very different rates. In the case of the white pupa strain, 3.5% recombinants were observed after rearing the strain for 15 generations. The second strain, utilizing white pupa and the temperature sensitive lethal as selectable markers, already reached a comparable level after six generations and was broken down completely in the ninth generation. In these strains the frequency of recombination is high because the breakpoint of T(Y;5)30C and the sexing gene(s) are far apart. To remedy the situation, we have isolated four new translocations with breakpoints located closer to the sexing genes. Mass rearing was simulated for several generations with strains based on these translocations and no breakdown was observed under the conditions used.

Sexual selection on multivariate phenotype in wild and mass-reared Ceratitis capitata (Diptera: Tephritidae)

“…A translocation T(Y:5) 2-22 (Franz et al, 1994) produces females with a white puparium and wild type male puparium, enabling to sort sexes at this stage. The lab pupae were produced at the BioKm8 facility (Mendoza, Argentina).…”

Practical Applications of Insects' Sexual Development for Pest Control

“…These are based on translocation of a dominant selectable marker to the Y chromosome [Bailey et al, 1980;Hendrichs et al, 1995;Franz et al, 1997;Robinson et al, 1999;Robinson, 2002;Yamada et al, 2012]. However, these translocations are unstable resulting in labour intensive and costly massrearing systems, despite much effort to minimise the problem [Franz et al, 1994;Kerremans and Franz, 1995;Franz, 2005]. Furthermore, each of these sexing strains must be developed anew for each new species [Alphey et al, 2008;Papathanos et al, 2009].…”

A repressible female-specific lethal genetic system for making transgenic insect strains suitable for a sterile-release program

“…Current medfly SIT programs use so-called ''genetic sexing strains'' that facilitate the large-scale separation of males from females (8). The strains are made by classical genetic methods involving the isolation of Y:autosome translocations, where the translocation carries a dominant wild-type allele for a selectable gene (9). For example, genetic sexing strains have been made that are homozygous for a recessive temperature-sensitive lethal allele on chromosome 5, and males carry a Y:5 translocation that includes a wild-type allele of the temperature-sensitive lethal gene (9).…”

“…The strains are made by classical genetic methods involving the isolation of Y:autosome translocations, where the translocation carries a dominant wild-type allele for a selectable gene (9). For example, genetic sexing strains have been made that are homozygous for a recessive temperature-sensitive lethal allele on chromosome 5, and males carry a Y:5 translocation that includes a wild-type allele of the temperature-sensitive lethal gene (9). In these genetic sexing strains, only male embryos survive incubation at the nonpermissive temperature.…”

“…In these genetic sexing strains, only male embryos survive incubation at the nonpermissive temperature. However, the strains can breakdown under mass rearing conditions because of male recombination (8,9). An alternative method of making a genetic sexing strain is to use genetic engineering (10).…”