Estimation of genetic parameters for growth and shell color traits in the tetraploid 'Haida No. 3' line of Pacific oysters (Magallana gigas) in China.

The Pacific oyster (Magallana gigas) is a widely cultivated species, and its commercial value has been significantly enhanced by the widespread adoption of triploid oysters. Since triploid offspring inherit two chromosome sets from tetraploid males, this suggests that genetic improvement of tetraploid oysters is essential. The induction of the dark-shelled tetraploid 'Haida No. 3' line from selected diploid lines of Pacific oysters has been achieved. However, the genetic parameters of growth and shell color traits in this line remain unclear. This study involved analyzing the genetic parameters of 42 tetraploid full-sibling families using the restricted maximum-likelihood (REML) method, with a tetraploid inverse additive relationship matrix constructed by the polyAinv package. These results indicated that the heritability of growth traits was moderate, with values ranging from 0.19 ± 0.05 for shell width to 0.45 ± 0.09 for whole weight. For shell color traits, the heritability values for color L*, color a*, color b*, and ΔE were 0.42 ± 0.09, 0.46 ± 0.09, 0.55 ± 0.10, and 0.63 ± 0.12, respectively. The genetic correlations ([Formula: see text]) between color L* and growth traits (excluding shell width) were moderate, ranging from 0.32 ± 0.15 to 0.42 ± 0.15. The low ΔE values observed across the tetraploid 'Haida No. 3' families indicate that the shell color purification has achieved the desired level of phenotypic consistency. Therefore, growth was identified as the primary breeding objective, with shell color regarded as secondary for the subsequent breeding program. The results provide useful information into selective breeding of fast-growing, black-shelled tetraploid oysters in aquaculture.