Linkage analysis of sex determination in Bracon sp near hebetor (Hymenoptera : Braconidae)

To test whether sex determination in the parasitic wasp Bracon sp, near heb etor (Hymenoptera: Braconidae) is based upon a single locus or multiple loc i, a linkage map was constructed using random amplified polymorphic DNA (RA PD) markers. The map includes 71 RAPD markers and one phenotypic marker, bl onde. Sex was scored in a manner consistent with segregation of a single "s ex locus" under complementary ses determination (CSD), which is common in h aplodiploid Hymenoptera. Under haplodiploidy, males arise from unfertilized haploid eggs and females develop from fertilized diploid eggs. With CSD, f emales are heterozygous at the sex locus; diploids that are homozygous at t he sex locus become diploid males, which are usually inviable or sterile. T en linkage groups were formed at a minimum LOD of 3.0, with one small linka ge group that included the sex locus. To locate other putative quantitative trait loci (QTL) for sex determination, sex was also treated as a binary t hreshold character. Several QTL were found after conducting permutation tes ts on the data, including one on linkage group I that corresponds to the ma jor sex locus. One other QTL of smaller effect had a segregation pattern op posite to that expected under CSD, while another putative QTL showed a fema le-specific pattern consistent with either a sex-differentiating gene or a sex-specific deleterious mutation. Comparisons are made between this study and the in-depth studies on sex determination and sex differentiation in th e closely related B. hebetor.