Allelic segregation of sex‐linked microsatellite markers in Nile tilapia (Oreochromis niloticus) and validation of inheritance in YY population

Abstract

Stocking of all-male fingerling produced by direct administration of male hormone 17-α-methyltestosterone is the most preferred method for present-day aquaculture of the Nile tilapia Oreochromis niloticus. However, due to the growing concern of negative impact of steroid hormone in food fish, production of ‘genetically male’ tilapia, which depends on the concrete and thorough understanding of sex determination, has long been a scientific curiosity. The objective of the present study was to identify reliable sex-linked markers and to evaluate the applicability of those markers in terms of monosex production approach. ‘XY’ neofemales were produced by using synthetic oestrogen and identified through selective breeding and progeny testing. Three females with progeny not deviating from 3:1 sex ratio (male:female) were designated as ‘XY’ neofemales and were used subsequently to produce putative YY progeny. Among the fifteen microsatellite markers tested, marker ARO172 was most informative in differentiating male and female genotypes. Twenty-seven F2 fish from three families were identified as putative YY males based on marker genotyping, and four of them were crossed to produce F3 to validate marker association by progeny testing. The YY males produced 86%–100% male progeny indicating ARO172 a unique sex-linked marker applicable in marker-assisted selection.