Further Analysis of Hybrid Dysgenesis in Drosophila melanogaster

Abstract

A systematic survey of the sterility of second-generation females produced by backcrossing hybrids of dysgenically interacting strains of D. melanogaster is reported. The effects of Fl rearing temperature and chromosomal constitution on this sterility were explicable in terms of the regulation of a transposable, inserted genetic element called the P factor which is known to be associated with hybrid dysgenesis. No applied radiation or chemical treatment induced dysgenic aberrations where they would not normally be found but, where they were found, EDT A slightly increased and ultraviolet radiation reduced their intensity. The results of previous temperature-shift experiments have implicated different periods during development as having the most effect on female'fertility. The present studies show little effect of interstrain variation on this critical period. Critical periods are identified for male sterility and recombination. Transmission ratio distortion has been shown to occur only in one of the reciprocal-cross hybrids (M x P) of parental strains causing dysgenesis. The degree of distortion in such crosses is shown here to vary between M strains crossed to the same P strain. Few data are available for the second (P x M) cross. The data reported here confirm that whatever distortion occurs in this cross is slight.