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

Abstract

Glossina morsitans submorsitans Newstead and Glossina morsitans morsitans Westwood carrying two marker genes on the X chromosome, two in linkage group II, and one in linkage group III were hybridized. About 17% of the F1 and from 33 to 56% of the backcross males fertilized G. m. submorsitans, but only one F1 and two backcross males fertilized G. m. morsitans. Similarly, F1 and backcross females were fertilized by G. m. submorsitans but rarely by G. m. morsitans. Chromosomal composition of F1 and backcross males indicated that hybrid male sterility is due to incompatibility of the X chromosome from one subspecies and the Y from the other subspecies or possibly an incompatibility between X chromosomes and autosomes from different subspecies. Results are discussed in the context of a model for evolution of X and Y incompatibility and a model for evolution of maternally inherited factors that cause unidirectional sterility in males. In hybrid females, intrachromosomal recombination was suppressed in the X chromosome and in linkage group II. Fertility of backcross females, mated to G. m. submorsitans, could not be related to the chromosomal composition of the females.Key words: Glossina, hybrid sterility, tsetse, X chromosomes.