草鱼生长性状的遗传参数和育种值估计

Estimation of genetic parameters and breeding values for growth traits in grass carp(Ctenopharyngodon idellus)

利用草鱼(Ctenopharyngodon idellus)生长性状选育核心群亲本,采用人工授精方式构建21个全同胞家系,并选用动物模型对16月龄草鱼生长性状进行遗传参数和育种值估计。结果显示,草鱼选育种群的生长性状存在丰富变异。采用约束极大似然法估计方差组分,发现草鱼体重、体长和体高性状的遗传力分别为0.39,0.47,0.21,属于中高遗传力;肥满度性状遗传力为0.11,属于低遗传力;4个性状的共同环境效应值相近且较小,范围为0.07~0.17。采用两性状动物模型分析相关性,发现体重、体长和体高性状间表型和遗传相关系数均达到高度正相关(r=0.88~0.97),而肥满度性状与三者间相关系数接近零,只与体高性状存在一定遗传正相关(r=0.43)。结合各性状遗传变异系数和相对遗传进度,分析表明,以体重为目标性状可便捷有效地改良草鱼生长性能。采用最佳线性无偏估计法预测个体育种值,发现4个性状育种值与表型值的相关系数范围为0.77~0.93。基于单性状育种值和表型值分别进行个体选择,按10%留种率,各性状选留个体相同率为68.75%~81.82%,秩相关系数范围为0.19~0.81,两种选择方式显示出较大差异,且差异大小与性状遗传力成反比例。本研究为草鱼生长性状选择育种提供了理论依据和技术支撑。

The objective of this study was to estimate genetic parameters and breeding values for growth traits in grass carp Ctenopharyngodon idellus, an important economic freshwater fish in China. A factorial mating design was carried out to construct 21 full-sib families by artificial fertilization, and their parents were from a nucleus breeding population. Animal models and REML procedures were used to estimate genetic, phenotypic, and environmental parameters for body weight （BW）, standard length （SL）, body height （BH）, and condition factor （K） for 16-month-old C. idellus. The results showed large variations for growth traits in the breeding population. Moreover, BW, SL, and BH traits displayed moderate to high levels of genetic variation （0.21 to 0.47） and relatively low heritability for condition factor （0.11）. In addition, common environmental effects were relatively low for the four growth traits （0.07-0.17）. Genetic and phenotypic correlations among BW, SL, and BH traits were all positive and ranged from 0.88 to 0.97. In contrast, the genetic correlations between K and BW or SL were close to zero, but not between K and BH （r=0.43）. Overall, the results suggested that BW could be a single target trait for the ge- netic improvement of growth performance in grass carp. The individual breeding values were predicted using the best linear unbiased prediction （BLUP） method with the software ASREML. Selection was practiced on individual phenotype or breeding values for each trait. The results showed that, although Pearson＇s correlations between breeding values and phenotypic values for each trait were 0.77-0.93, the same selected individual rates for each trait ranged from 68.75% to 81.82%, and Spearman＇s correlation coefficients ranged from 0.19 to 0.81 at a 10% selection intensity. Both methods of selection presented significant differences, particularly for the trait with low heritability. This study provides a theoretical basis and technical support for selective breeding of growth traits in grass carp.