Genetic basis of hybrid male sterility among three closely related species of <i>Drosophila</i>

Abstract

The genetic basis of hybrid male sterility among three closely related species, <i>Drosophila bipectillala</i>, <i>D. parabipectinata </i>and <i>D. malerkotliana </i>has been investigated by using backcross analysis methods. The role of Y<i> </i>chromosome, major hybrid sterility (MHS) genes (genetic factors) and cytoplasm (non-genetic factor) have been studied in<i> </i>the hybrids of these three species. In the species pair, <i>bipectinata </i>- <i>parabipectinata, </i>Y chromosome introgression of<i> parabipectinata</i> in the genomic background of <i>bipectinata </i>and the reciprocal Y chromosome introgression were<i> </i>unsuccessful as all males in second backcross generation were sterile. Neither MHS genes nor cytoplasm was found<i> </i>important for sterility. This suggests the involvement of X-Y, X-autosomes or polygenic interactions in hybrid male sterility.<i> </i>In <i>bipectinata</i> - <i>malerkotliana</i> and <i>parabipectinata </i>- <i>malerkotliana</i> species pairs, Y chromosome substitution in reciprocal<i> </i>crosses did not affect male fertility. Backcross analyses also show no involvement of MHS genes or cytoplasm in hybrid<i> </i>male sterility in these two species pairs. Therefore, X- autosome interaction or polygenic interact ion is supposed to be<i> </i>involved in hybrid male sterility in these two species pairs. These findings also provide evidence that even in closely related<i> </i>species, genetic interactions underlying hybrid male sterility may vary.