دانلود رایگان مقاله برآورد پارامترهای ژنتیکی صفات رشد با ارتباط مولکولی در سپر ماهی

Abstract

Turbot (Scophthalmus maximus, Linnaeus, 1758) is an important aquaculture species in China, however, selective turbot breeding is restricted because there is no reliable pedigree data. The objective of this study was to evaluate the performance of a molecular relatedness method to estimate genetic parameters for growth traits in turbot. The experimental population consisted of 843 15-month-old turbot from 79 full-sib families produced via fertilization involving 50 sires and 34 dams. Twenty unlinked microsatellite loci in this population were genotyped to calculate their molecular relatedness. Both molecular relatedness and pedigree were used to construct an additive genetic matrix to apply to the same animal model and estimate genetic parameters and breeding value. Thereafter, we compared the accuracy of two estimators by cross validation. Heritability for body weight and length were 0.33 ± 0.15 and 0.24 ± 0.14, respectively, based on pedigree and both were 0.23 ± 0.04 based on molecular relatedness. Genetic correlation and phenotypic correlation were 0.96 ± 0.02 and 0.87 ± 0.01, respectively, based on molecular relatedness and 0.99 ± 0.02 and 0.89 ± 0.01, respectively, based on pedigree. Cross validation revealed that the accuracy of estimated breeding values was 0.85 with pedigree and 0.92 with molecular relatedness. These results suggest that molecular relatedness is a feasible approach to genetic parameter estimation when pedigree information is either inaccurate or absent. Statement of relevance: The authors have declared that no commercial aquaculture exists

4.2. Genetic analysis

The animal model containing common environmental effects used in this study proved to be an optimal model to estimate turbot genetic parameters (Guan et al., 2016; Ma et al., 2009). The fixed effect of sex was nonsignificant. This was in agreement with previous research. Although female turbot had higher body weight than males, the difference was not significant in the early stage (Wang et al., 2014). The day-age was the same in all individuals, therefore, the day-age covariant was omitted from the model. Heritability estimates for BW and BL obtained from both methods were all medium in 15 month-old turbot, based on the following categorization: low (0.05–0.15), medium (0.20–0.40), high (0.45–0.60), and very high (N0.65) (Cardellino and Rovira, 1987). A limited number of studies have reported on the estimation of growth trait heritability in turbot. Ma et al. (2008, 2009) estimated heritability for growth traits in turbot, they reported 0.450–0.514 for BW and 0.251–0.425 for BL in 6- month-old fish, and 0.34 for BW in 15-month-old fish. Both Liu et al. (2011) and Guan et al. (2016) estimated heritability for BW in 100 juvenile turbot and obtained 0.22 and 0.19, respectively. The results from both methods in our study were close to those reported in earlier studies. What calls for attention is that selecting 40 largest body weigh individuals from each family at 3 months post hatching induced a slight bias to the estimation of heritability potentially, because it might increase resemblance of the family members. Heritability and standard error based on molecular relatedness were slightly lower than pedigree, because molecular relatedness estimated a smaller genetic variance.