壳白长牡蛎品系生长和壳色性状遗传参数估计

以经过连续4代家系选育获得的壳白长牡蛎(Crassostrea gigas)选育系为亲本,通过巢氏平衡设计建立了30个全同胞家系混合养殖,采用微卫星多重PCR技术进行家系鉴定,基于REML法估算24月龄壳白长牡蛎的生长性状和壳色性状的遗传参数。结果表明,壳白长牡蛎品系壳高、壳长、总重、壳重、L~*(明度)、a~*(红绿轴色品指数)和b~*(黄蓝轴色品指数)的遗传力为中高等水平,依次为0.35±0.13、0.18±0.09、0.20±0.09、0.16±0.08、0.16±0.08、0.27±0.11和0.19±0.08,壳宽、肉重、出肉率、壳型指数A和壳型指数B的遗传力为低等水平,依次是0.07±0.02、0.11±0.06、0.02±0.03、0.08±0.06和0.11±0.06。壳高、壳长、壳宽、总重、壳重和肉重之间的遗传相关和表型相关均为正相关,其中,壳高、壳宽和总重与其他生长性状的相关性较高,分别为0.40±0.65~0.90±0.14、0.39±0.55~0.97±0.24和0.50±0.66~0.99±0.02。壳型指数A和壳型指数B与壳高均为较高的负相关,分别为–0.94±0.16和–0.77±0.19,表明仅以壳高性状为选育目标时,可能不会对长牡蛎壳型改良产生作用。壳白长牡蛎壳色参数与生长性状之间的遗传相关范围为–0.09±0.42~0.91±0.74,不同性状间的遗传相关差异很大,其中L~*与生长参数遗传相关较高,为0.49±0.29~0.91±0.74,表明以壳高、壳长、总重和L~*任一个为选育目标时,其他生长性状都可以获得提高。壳色参数间L~*与a~*负的相关性最高,为–0.96±0.04,L~*与b~*和a~*与b~*相关性较低,分别为–0.08±0.36和0.21±0.31,表明以L~*为选育目标时,可间接降低a~*值。本研究为合理制定壳白长牡蛎新品系育种方案和选择反应预测提供了参考依据。

Estimates of genetic parameters for growth and shell color traits in the white-shell strain of Pacific oyster (Crassostrea gigas)

The Pacific oyster (Crassostrea gigas) is the most widely cultured shellfish in the world. There is considerable focus on improving selective breeding procedures for economic traits. We used specimens of the white-shell strain of C. gigas after four generations of family selection as parents to construct 30 full-sib families in a nested design. A mixed family approach combined with parentage analysis using highly polymorphic microsatellite makers and REML based on the animal model was used to estimate genetic parameters of white-shell C. gigas at the age of 24 months. The results showed that heritabilities of shell height, shell length, total weight, shell weight, L^*, a^*, and b^* were 0.35±0.13, 0.18±0.09, 0.20±0.09, 0.16±0.08, 0.16±0.08, 0.27±0.11, and 0.19±0.08, respectively. Shell width, meat weight, meat ratio, and indexes A and B of shell shape showed lower heritabilities of 0.07±0.02, 0.11±0.06, 0.02±0.03, 0.08±0.06, and 0.11±0.06, respectively. All phenotypic and genetic correlations among shell height, shell length, shell width, total weight, shell weight, and meat weight were positive. Genetic correlations were higher between shell height, shell length, total weight, and the other growth traits, ranging from 0.40±0.65 to 0.90±0.14, 0.39±0.55 to 0.97±0.24, and 0.50±0.66 to 0.99±0.02, respectively. Genetic correlation between index A of shell shape and shell height was -0.94±0.16, and -0.77±0.19 between index B of shell shape and shell height, suggesting that shell shape would not change if just shell height were selected in breeding programs. Genetic correlations were significantly different between shell color traits and growth traits, varying from -0.09±0.42 to 0.91±0.74. Higher genetic correlations between L^* and growth traits indicated that direct selection on L^* (the same as shell height, shell length, and total weight) could improve other growth traits. There was a negative genetic correlation between L^* and a^* of -0.96±0.04. Conversely, genetic correlations were lower between L^* and a^*, and between a^* and b^*, suggesting that selection to improve L^* could also decrease a^*. This information will benefit genetic improvement of the white-shell strain of C. gigas.