Sterility Principle for Insect Control or Eradication

Abstract

The introduction of chromosome translocations into tsetse populations is expected to cause a serious depression of fertility because of the semi sterility of the heterozygotes. It would only be practicable to mass-rear the translocations in the form of fertile homozygotes. Mutations with the properties of translocation heterozygotes were obtained in Glossina austem by madiation and selection for semi Sterility. The descendants of such mutant individuals were inbred to try to produce homozygotes. A suitable translocation would show full fertility when the homozygote was mated to wild type and all the products of such mating would be semi sterile heterozygotes. Two generation tests for these properties were used to diagnose translocation homozygotes among the products of inbreeding. About 300 individuals belonging to 7 different mutant stocks were tested and in three of the stocks translocation homozygote individuals were fairly certainly identified. In one of the mutant Lines n was possible to mate individuals identified as translocation homozygotes to close relatives and, as expected, this produced several translocation homozygotes and heterozygotes and one unexplained Wild type. Further inbreeding in these families has yielded some fully fertile mating’s which are expected to be the founders of pure translocation homozygote families. There are preliminary indications of reduced viability in these families but n IS not yet clear whether this IS due to recessive effects of the translocation nse1f, or to the effects of the intense inbreeding to which they have been submitted. Two of the mutant lines originally showed transmission of semi sterility to a proportion of both sexes, but, after several generations of inbreeding and selection, semi sterility is now transmitted to all males and no females. It may be that in these lines the effect of selection at each generation for semi sterile males has been to transfer the sex-determining function from the X and Y chromosomes to a locus at or linked to the translocation break points.