Investigation of quantitative trait loci (QTL) variations for growth-related traits in farmed rainbow trout (Oncorhynchus mykiss)

In this study thirty male and female broodstock of rainbow trout (n=30) for generating full sibling collected in Cold-water Fishes Genetic and Breeding Research Center. We generated 13 different families using factorial mating design. Then juveniles were raised at the ponds until 6 months post-hatching. Genome extracted based on standard method and these individuals randomly selected for molecular analysis. Fin clips were cut and specimens were kept at -20̊ C until use. Four specific primers were used for rainbow trout and all the four QTL loci screened in this study were successfully amplified in all families. Statistical analyses including linkage disequilibrium (LD), association between genotypes and two quantitative traits including body weight (BW) and total length (TL) were performed using MapChart 2.1, GDA 1.1. General Linear Model (GLM) was performed with software SPSS 21.0. The results demonstrated the mean observed heterozygosity (Ho) and expected heterozygosity (HE) varied between 0.354 to 0.699 for locus OMM5140 and 0.568 to 0.836 for locus OMM1268, respectively. No significant epistatic interactions were identified between QTL markers. Proportion of phenotypic variation explained by each QTL (PV) for body weight at age 30 and 180 were 18.48 and 31.24, respectively. Hardy-Weinberg departure was observed for most loci from all farms and were disequilibrium (p < 0.05). The four QTL loci variation in rainbow trout is important to gain a better understanding of the genetics of production traits and for transferring genetic information and improved selective breeding program to farms in Iran