Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2004
Publication Date: 4/15/2005
Citation: Marec, F., Neven, L.G., Robinson, A.S., Vreysen, M., Goldsmith, M.R., Nagaraju, J., Franz, G. 2005. Development of genetic sexing strains in Lepidoptera: From traditional to transgenic approaches. Journal of Economic Entomology. 98:248-259. Interpretive Summary: The sterile insect technique (SIT) is a method currently used to eradicate or suppress pest species populations. SIT relies upon the mating of mass released sterile males with the incipient populations' females. However, the release of only males from mass rearing facilities is very difficult due to inability or cost of separating the sexes. Traditionally sexing methodologies have relied on the development of genetic mutations to discern males from females. These methods use irradiation or chemicals to cause chromosomal translocations, and use at least two lines which must be maintained to create the sexing strain. Hence, these sexing methods can be very expensive and difficult to maintain and monitor in a mass rearing system. Recent research in insect transgenesis has led to the development plan for a new method to create genetic sexing lines in Lepidoptera. This plan details how transgenesis of the sex determining chromosome of female Lepidoptera, which is the heterogametic sex, can be targeted for transformation with a marker gene and a temperature sensitive dominant conditional lethal mutation. This paper explains the current technology for development of genetic sexing lines as well as this transgenic plan and how it can be used to improve SIT for Lepidoptera.
Technical Abstract: The Sterile Insect Technique (SIT) is currently being used for the control of many agricultural pests including some lepidopteran species. The SIT relies on the rearing and release of large numbers of genetically sterile insects into a wild population. The holokinetic chromosomes of Lepidoptera respond differently to radiation than do species where there is a localized centromere. This difference has enabled a variation of the SIT to be developed for Lepidoptera where a sub-sterilizing dose of radiation is given to the insects prior to their release with the result that a certain level of sterility is inherited by the F1 offspring. Both conventional SIT and radiation-induced inherited sterility (IS) would benefit if efficient ways could be found to release only males, and approach that has been demonstrated for some dipteran pest species. This paper outlines Mendelian approaches that are currently available to separate large numbers of males and females efficiently for different lepidopteran species and describes their difficulties and constraints. The fact that transgenesis can now be carried out in several lepidopteran species opens up new possibilities to develop genetic sexing strains. The proposal to develop genetic sexing strains described in this paper takes advantage of the fact that in Lepidoptera, the female is the heterogametic sex, with most species possessing a WZ sex chromosome pair, while the males are ZZ. This means that if a conditional lethal gene can be inserted into the W chromosome then all females should die following the application of the restrictive condition. The assumptions made to accommodate this model are discussed and the advantages to be gained for control programs elucidated.