Association between polymorphism in the Prolactin I promoter and growth of tilapia in saline-water

Abstract Tilapias are a group of species with a variable tolerance to high salinity, which are cultured worldwide in fresh, brackish and seawater. Prolactin I ( PRL I ) is known as a key hormone in osmoregulatory physiological pathways. A previous study, conducted in a single family, reported on association between polymorphism in a repetitive element within the promoter of the PRL I gene and growth rate of tilapia in saline water. This study was aiming to further validate this association in a larger sample size, and was conducted in nine families over two consecutive breeding seasons. We have confirmed this association in the three F 2 families of Oreochromis mossambicus  ×  Oreochromis niloticus hybrids challenged in the first year. The same pattern of improved growth for genotypes with shorter alleles originating from the O. niloticus grand-parental fish, although O. mossambicus is considered to be a more salt tolerant species, was demonstrated. The effects accounted for 13–15% of the phenotypic variance for growth rate ( P PRL I promoter and the expression of the gene.