Sexual competitiveness of a transgenic sexing strain of the Mediterranean fruit fly, Ceratitis capitata

Abstract

AbstractThe sterile insect technique (SIT), when used for the control of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), generally relies on the release of sterile flies of only the male sex. Male selection is achieved through the use of a genetic sexing strain (GSS) in which females are killed by heat treatment in the generation prior to release. Transgenic sexing strains (TSS) have been developed that perform the same function of female‐lethality, this time by withholding tetracycline (or related compounds) from the larval diet. The use of TSS may allow for certain problems associated with conventional GSS, such as strain instability and reduced productivity in mass‐rearing, to be avoided. The performance, and principally the sexual competitiveness, of released male flies is important for the success of an SIT control programme. This study describes field cage experiments in which the competitiveness of males from a TSS (OX3376B) was compared with that of a conventional GSS (VIENNA‐8) and two wild‐type strains (TOLIMAN and ARG). When competing for female mates with wild‐type males, OX3376B male performance was acceptable. When OX3376B males competed directly for mates with VIENNA‐8 males, VIENNA‐8 slightly outperformed the TSS males. Parallel tests, in which wild‐type males competed with either OX3376B or VIENNA‐8 males, showed that males from both sexing strains were highly competitive with wild‐type males. These results suggest that OX3376B in particular, and TSS in general, show sufficiently good mating competitiveness to merit further research into their suitability for eventual use in SIT programmes.