Sex determination in the genus Oreochromis: 1. Sex reversal, gynogenesis and triploidy in O. niloticus (L.)

Citation

Mair GC, Scott AG, Penman D, Beardmore JA & Skibinski DOF (1991) Sex determination in the genus Oreochromis: 1. Sex reversal, gynogenesis and triploidy in O. niloticus (L.). TAG Theoretical and Applied Genetics, 82 (2), pp. 144-152. https://doi.org/10.1007/BF00226205

Abstract
Established techniques of genetic manipulation were used to elucidate sex-determining mechanisms in the commercially important tilapia, Oreochromis niloticus. Analysis of sex ratios from single-pair matings of normal broodstock showed these to be heterogeneous, with an asymmetrical frequency distribution. Data were homogeneous, with the exclusion of a number of broods with sex ratios not significantly different from 3∶1 (male: female), and further progeny testing revealed atypical female heterogamety in the parents of these broods. Analysis of sex ratios from complete diallele-type crosses using five males and five females demonstrated no association between male parent, female parent and progeny sex ratio. Sex ratios of gynogens (0∶1) and triploids (1∶1), and from progeny testing of sex-reversed males (0∶1) and sex-reversed females (3∶1), provide evidence for female homogamety in this species. Progeny testing of male gynogens derived from sex-reversed females demonstrated recombination between the centromere and the sex-determining locus (68.9%). Novel YY "supermales" were shown to be viable and produced all-male offspring. It was concluded that this species exhibits monofactorial, genotypic sex determination with male heterogamety. However, rare autosomal or environmental sex-modifying factors may account for occasional deviations from expected sex ratios.

Keywords
Sex determination; Oreochromis niloticus; Gynogenesis; Sex reversal; Triploidy

Journal
TAG Theoretical and Applied Genetics: Volume 82, Issue 2