Matt Joseph L, Small Jessica Moss, Kube Peter D, Allen Standish K
Marine Genomics Lab, Department of Life Sciences, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX, 78412, USA.
Texas A&M AgriLife Research, 600 John Kimbrough Boulevard, Suite 512, College Station, TX, 77843, USA.
Genet Sel Evol. 2025 Apr 9;57(1):19. doi: 10.1186/s12711-025-00965-3.
Triploid oysters, bred by crossing tetraploid and diploid oysters, are common worldwide in commercial oyster aquaculture and make up much of the hatchery-produced Crassostrea virginica farmed in the mid-Atlantic and southeast of the United States. Breeding diploid and tetraploid animals for genetic improvement of triploid progeny is unique to oysters and can proceed via several possible breeding strategies. Triploid oysters, along with their diploid or tetraploid relatives, have yet been subject to quantitative genetic analyses that could inform a breeding strategy of triploid improvement. The importance of quantitative genetic analyses involving triploid C. virginica has been emphasized by the occurrence of mortality events of near-market sized triploids in late spring.
Genetic parameters for survival and weight of triploid and tetraploid C. virginica were estimated from twenty paternal half-sib triploid families and thirty-nine full-sib tetraploid families reared at three sites in the Chesapeake Bay (USA). Traits were analyzed using linear mixed models in ASReml-R. Genetic relationship matrices appropriate for pedigrees with triploid and tetraploid animals were produced using the polyAinv package in R.
A mortality event in triploids occurred at one site located on the bayside of the Eastern Shore of Virginia. Between early May and early July, three triploid families had survival of less than 0.70, while most had survival greater than 0.90. The heritability for survival during this period in triploids at this affected site was 0.57 ± 0.23. Triploid survival at the affected site was adversely related to triploid survival at the low salinity site (- 0.50 ± 0.23) and unrelated to tetraploid survival at the site with similar salinity (0.05 ± 0.39).
Survival during a late spring mortality event in triploids had a substantial additive genetic basis, suggesting selective breeding of tetraploids can reduce triploid mortalities. Genetic correlations revealed evidence of genotype by environment interactions for triploid survival and weak genetic correlations between survival of tetraploids and triploids. A selective breeding strategy with phenotyping of tetraploid and triploid half-sibs is recommended for genetic improvement of triploid oysters.
通过四倍体牡蛎与二倍体牡蛎杂交培育出的三倍体牡蛎在全球商业牡蛎养殖中很常见，并且在美国大西洋中部和东南部养殖的孵化场生产的弗吉尼亚牡蛎中占了很大比例。通过培育二倍体和四倍体动物来对三倍体后代进行遗传改良是牡蛎特有的做法，并且可以通过几种可能的育种策略来进行。三倍体牡蛎及其二倍体或四倍体亲属尚未接受过能够为三倍体改良育种策略提供信息的数量遗传学分析。晚春时节接近上市规格的三倍体牡蛎出现死亡事件，这凸显了对弗吉尼亚三倍体牡蛎进行数量遗传学分析的重要性。
从在美国切萨皮克湾三个地点养殖的20个父本半同胞三倍体家系和39个全同胞四倍体家系中估计三倍体和四倍体弗吉尼亚牡蛎的存活和体重的遗传参数。使用ASReml-R中的线性混合模型对性状进行分析。使用R中的polyAinv软件包生成适合三倍体和四倍体动物谱系的遗传关系矩阵。
在弗吉尼亚州东海岸海湾一侧的一个地点，三倍体牡蛎发生了死亡事件。在5月初至7月初期间，三个三倍体家系的存活率低于0.70，而大多数家系的存活率高于0.90。在此受影响地点，三倍体在此期间存活的遗传力为0.57±0.23。受影响地点的三倍体存活率与低盐度地点的三倍体存活率呈负相关（-0.50±0.23），与盐度相似地点的四倍体存活率无关（0.05±0.39）。
三倍体在晚春死亡事件期间的存活具有显著的加性遗传基础，这表明对四倍体进行选择性育种可以降低三倍体的死亡率。遗传相关性揭示了三倍体存活存在基因型与环境相互作用的证据，以及四倍体和三倍体存活之间的弱遗传相关性。建议采用对四倍体和三倍体半同胞进行表型分型的选择性育种策略来对三倍体牡蛎进行遗传改良。
