大菱鲆(Scophthalmus maximus)不同生长阶段体重的遗传参数和育种值估计

GENETIC PARAMETERIZATION FOR TURBOT SCOPHTHALMUS MAXIMUS:IMPLICATION TO BREEDING STRATEGY

采用非求导约束最大似然法(DFREML)进行了大菱鲆不同生长阶段体重的遗传参数和育种值研究,每一生长阶段分别对4种不同动物模型估计遗传参数的差异进了比较。不同模型中对全同胞家系效应和日龄协变量作了不同的考虑:模型A,不考虑全同胞家系效应和日龄协变量;模型AD,仅考虑日龄协变量;模型AF,仅考虑全同胞家系效应;模型AFD,同时考虑全同胞家系效应和日龄协变量。结果表明,6月龄利用模型AF,3月龄、9月龄、12月龄、15月龄利用模型AFD对遗传参数和育种值进行估计较为适合。利用育种值选择和表型值选择两种方法分别进行了家系选择和个体选择的效率比较,结果表明,在每一生长阶段依据育种值选择的效率均高于表型值选择的效率。利用不同生长阶段的家系育种值以及亲本育种值分别进行了家系选择比较和亲本选择比较,结果表明,在不同生长阶段,按家系、父本和母本的育种值分别排序,前50%的相同率和育种值的相关系数均为9—12月龄较6—9月龄的提高幅度比其它相邻阶段显著增加,推测家系提前筛选的时间以及父本和母本选择的时期均不低于9月龄。

To accurately estimate the genetic parameters and breeding values of body weight of turbots, four different animal models were compared in body weight at different growth stages （from 3 to 15 months） for 56 full-sib families. The four models were designed in the combination of using full-sib family effect and/or family age as covariate： in Model A both the family effect and family age are ignored, in Model AD only family age is used, in Model AF only the family effect is considered, and in Model AFD both the family effect and family age are included. The variance components in different models are estimated with derivative-free restricted maximum likelihood （DFREML） method and the MTDFREML program. Differences among the models are tested by likelihood ratio test. The results show that the optimal model for 6-month-old sample is AF model, and that for the 3-, 9-, 12- and 15-month-old samples is AFD model. The breeding values of body weight at each growth stage are predicted with the best-fit models, and the efficiency of family selection and individual selection are compared with breeding value selection and phenotypic selection. Results indicate that, whether for family selection or individual selection, the efficiency of breeding-value-based selection is higher than that of phenotypic selection. At different growth stages, the average breeding values of family and parent are used are compared with those of family selection and parent selection. The results show that all the uniformity ratio of the first 50% families, sires, dams are different statistically from the breeding values estimated with the optimal models for body weighs at different growth stages; the relation between the ratio and the breeding value for the 9-12-month-old samples are the strongest. Therefore, the selection of family and sires/dams should be conducted on the fish in 9 months.