Sex‐determining genes in tilapia: a model of genetic recombination emerging from sex ratio results of three generations of diploid gynogenetic Oreochromis aureus

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Abstract
Three major findings emerged from this study: (1) the existence of gynogenetic males among first, second and third generations of gynogenetic tilapias; (2) the sex ratios amongst gynogenetic offspring reflect two genetically different maternal types, the first type giving rise to both gynogenetic males and females, and the second type only to females; (3) females of the first maternal type produce more gynogenetic female than male offspring. On the basis of a genetic recombination model between sex‐determining genes and the centromere, the first maternal type was defined as heterogametic (WY) and the second as homogametic (WW). This model suggests that females with the WY combination can produce in all descending gynogenetic generations offspring expressing the three above gynotypes, and this suggestion is consistent with our FI–F3 sex ratio results.