Genotype by environment (G×E) interaction for growth and shell color traits in the white-shell strain of Pacific oyster (Crassostrea gigas)

The purpose of the present study is to reveal the genotype by environment (G×E) interactions on growth and shell color traits in the white-shell strain of Pacific oyster (Crassostrea gigas). The specimens of the white shell strain of C. gigas under six-generation of selection as parents were used to construct full-sib families following the method of nested design. All families were divided into two batches and grown in two environments, Rushan and Rongcheng. Linear mixed model and REML method based on an animal model were applied to estimate genetic parameters of white shell C. gigas at the age of 11 months. The best linear unbaised prediction (BLUP) method was used to estimate breeding values for shell height and L*, and superior families were selected based on comprehensive estimated breeding values. The results showed that heritabilities for growth and shell color traits in Rushan ranged from 0.14±0.08 to 0.62±0.18, while these were different in Rongcheng, varying from 0.01±0.03 to 0.78±0.19, which indicated that G×E interactions might be present as scale effects. After integrating the data in two different environments, heritabilities for growth and shell color traits ranged from 0.02±0.02 to 0.51±0.09. However, the estimates of heritabilities might be over-estimated because maternal/common environmental effects and dominance effects were included in the estimation model due to absence of some families and convergence problem. Genetic correlations for all growth and shell color traits between two environments, ranging from –0.47±0.40 to 0.75±0.18, were less than 0.8. This suggested that G×E interactions in the form of re-ranking of families across environments was apparent. It will be necessary to select lines that are suited to particular sites. The top 20 offspring in the rank of comprehensive estimated breeding values derived from different families in two different environments, indicating that the different families performed differently across the different rearing sites. The families G1 and G21 performed better in Rushan area, while the G4, G22 and G5 were most excellent families in Rongcheng area, and familiy G2 had high adaptability to both sites. The information obtained in this study will benefit genetic improvement of the white shell strain of C. gigas.