Genetic analysis of sterility in hybrids from crosses of Glossina morsitans submorsitans and Glossina morsitans centralis (Diptera: Glossinidae)

Abstract

When genetically marked Glossina morsitans submorsitans Newstead were mated to Glossina morsitans centralis Machado, viable offspring were obtained when using G. m. submorsitans females but not when using G. m. centralis females. The maternally inherited sterility factor, from G. m. submorsitans, that causes this asymmetry was inactivated or replaced during recurrent backcrossing to G. m. centralis. F1 hybrid males were sterile but most F1 hybrid females were fertile. There was little evidence for differential transmission of G. m. submorsitans and G. m. centralis chromosomes by hybrid females. Almost all backcross males were sterile if they had an X and a Y chromosome from two different taxa; the exceptional males had recombinant X chromosomes. The X chromosome locus for X/Y compatibility lies closer to the locus for esterase-X than to the locus for glucose-6-phosphate dehydrogenase. Heterozygosity in linkage group II is also a factor in causing hybrid male sterility; the locus for compatibility is closer to the locus for octanol dehydrogenase than to the locus for esterase-1. Among the backcross males that had an X and a Y chromosome from the same taxon, 12% of those obtained by backcrossing to G. m. centralis were fertile and 65% of those obtained by backcrossing to G. m. submorsitans were fertile. Backcrossing F1 hybrid females to G. m. submorsitans produced females that were equally likely to be fertilized by G. m. submorsitans and G. m. centralis. However, backcrossing to G. m. centralis produced females that had a much lower probability of being fertilized by G. m. submorsitans than by G. m. centralis.