EXPLORING THE POTENTIAL OF COMPOUND;FREE-ARM COMBINATIONS OF CHROMOSOME 2 IN DROSOPHILA MELANOGASTER FOR INSECT CONTROL AND THE SURVIVAL TO PUPAE OF WHOLE-ARM TRISOMIES

Genetic tests of second-chromosome compound;free-arm combinations ("free arms") in Drosophila melanogaster indicate that the egg hatch is approximately 50% that of standard lines and adult recovery is approximately 40%. Free-arm strains are genetically isolated from both compound-chromosome lines and standards. A large proportion of the hybrid progeny arising from crosses between free arms and standards or free arms and compounds, survive to the pupal stage. Cytological examinations reveal that these hybrids are trisomic for one arm of chromosome 2. Such hybrid progeny may place an added constraint upon the competition between free-arm and standard strains by competing for food, but not contributing to the adult population. The fitness data, the genetic isolation characteristic and the possible impact of hybrid progeny all suggest that free arms may prove to be a valuable genetic tool for insect population control. Preliminary cage-competition experiments to test this prediction have demonstrated that free arms are able to displace standards at ratios as low as 3:1, which is close to the theoretical equilibrium predicted by the fitness data (2.5:1).