Meiotic disjunction and embryonic lethality in sex-linked double-translocation heterozygous males of the onion fly,Hylemya antiqua (Meigen)

Summary The frequencies of disjunction types in double-translocation heterozygous males (2⁶2^Y6²6XY²) in Hylemya antiqua have been established in MII cells and eggs of testcrosses.Several disjunction types occurred but four predominated. A correlation was found between the frequencies of the disjunction types and the relative position of the centromeres. The frequency of numerical non-disjunction (NND) was 4%. Differences in frequency of NND between sex-linked and autosomal translocations of H. antiqua are discussed. A good correspondence between the frequencies of unbalanced karyotypes, and embryonic and larval mortality was found. The total genetic load which can be induced by the T14/T61 males is estimated to be 60–65%. Some duplication/deficiency karyotypes appeared to be viable in pupal and even adult stages. In 2⁶2⁶2^Y6²6²X males a regular coorientation between 2^Y and X was observed, in spite of non-homologous centromeres and a complicated synapsis of 2^Y. Application possibilities of the present material for genetic control of H. antiqua are discussed.