虹鳟生长性状的随机回归分析

生长和抗逆是水产动物遗传育种工作中最重要的农艺性状,虹鳟的生长性状关乎虹鳟规模化养殖的生产经济效益,为了从遗传上精细解析虹鳟的生长性状,我们从渤海、丹麦、挪威、唐纳森和加利福尼亚5个虹鳟(Oncorhynchus mykiss)种系间的双列杂交开始,进行了连续4代的继代选育。本研究测量了第4代总共4368个实验个体在516日龄、608日龄、668日龄、883日龄和1036日龄5个时间点的生长数据。采用随机回归测定日模型,对虹鳟生长性状进行了动态遗传分析。根据贝叶斯信息准则,确定3阶勒让德多项式为拟合体重和体长的加性遗传效应和永久环境效应变化的最优子模型。利用双变量随机回归模型同时分析体重和体长两个生长性状。它们的遗传力在400～1000日龄之间呈现递减趋势,分别从0.288下降到0.164和从0.469下降到0.186,并且在该生长区间内体长的遗传力始终高于体重的遗传力。无论体重还是体长性状,在不同日龄之间的遗传相关都随着生长间隔的增大而降低,但是两个性状在生长初期和后期之间的遗传相关较高(遗传相关系数0.75以上),尤其是体重(遗传相关系数0.85以上),该研究结果为虹鳟早期的遗传选育提供了理论支撑。两个性状之间在相同日龄之间的遗传相关均在0.75以上,在不同日龄之间的遗传相关随着生长间隔的增大由0.83下降到0.63。以上的研究结论为虹鳟生长性状(主要是体长和体重)的遗传选育提供了理论基础,同时也为虹鳟的体长和体重两个性状的联合选育提供了精确的遗传分析结果,由于两性状在前期有较高的遗传相关,因此建议在虹鳟生长前期(400日龄)进行联合选择。

Random regression analysis for growth traits in rainbow trout (Oncorhynchus mykiss)

Growth and resistance are the most important agricultural traits for genetic breeding in aquaculture animals. The growth trait of Rainbow trout is central to the economic development in scaled production. Launched from strains of Bohai, Denmark, Norway, Donaldson and California, family selection of the rainbow trout was performed for four consecutive generations based on biallele crossing design. Only data from the fourth generation was selected for this study. Dynamic genetic analysis was conducted using 19299 records repeated body weight (BW) and body length (BL) measurements, which were obtained to genetically evaluate the growth traits of 4368 samples for the fourth generation at their 516 days of age, 608 days of age, 668 days of age, 883 days of age and 1036 days of age. According to the Bayesian information criterion (BIC), Legendre polynomials of three orders were selected as the most optimized submodel to fit changes in additive genetic and permanent environmental effects on both BW and BL. With a bivariate random regression model (RRM), both traits were analysed simultaneously. The heritabilities were estimated to exhibit a downward tendency between 400 and 1000 days of age, from 0.288 to 0.164 and from 0.469 to 0.186 for BW and BL, respectively, while BL was inherited in a consistently higher manner than BW. The genetic correlation of BW and BL showed a tendency towards the decrease of heritabilities with the enlarged growth space. However, the traits in the initial and later days of age showed higher correlation for both traits which are all above 0.75, especially for BW, which is higher than 0.85. The genetic correlations in the same growth days of age for both traits are equal to or above 0.75, but decreased from 0.83 to 0.63 in different growth days of age. In summary, the genetic correlation of a single trait or both traits between paired day-ages decreased with the increasing age-interval. However, the consistent genetic correlation between paired day-ages makes the genetic selection for BW feasible at an early stage. These results provide the theoretical basis for breeding selection focused on BW and BL growth traits. At the same time, this research also provides accurate genetic analysis results which is most fitted for the combined selection. Due to the existing higher genetic correlations between early and later stage for BW and BL, the combined selection is suggested from early 400-growth-day. In addition, the big population with couple families will be artificially divided into several individual subpopulations and repeated random measurements for growth points series will be executed for every subpopulation. This technique will satisfy the requirements for an improved fitting with the growth curve and also save money, including from decreased labour costs.