Responses to two-way selection on growth in mass-spawned F_1 progeny of Argopecten irradians concentricus(Say)

In the present study, the effect of one-generation divergent selection on the growth and survival of the bay scallop （Argopecten irradians concentricus） was examined to evaluate the efficacy of a selection program currently being carried out in Beibu Bay in the South China Sea. A total of 146 adult scallops were randomly selected from the same cultured population ofA. i. concentricus, and divided into two groups in shell length （anterior-posterior measurement）： large （4.91-6.02 cm, n=74） and small （3.31-4.18 cm, n=72）. At the same time, a control group was also randomly sampled （4.21-4.88 cm, n=80）. Mass-spawned F1 progenies from the three size groups were obtained and reared under identical conditions at all growth phases. The effects of two-way （or upward-downward） selection on fertilization rate, hatching rate, survival rate, daily growth in shell length and body weight were assessed in the three size groups. Results show that significant differences （P〈0.01） were found in hatching rate, survival rate and daily growth of F~ progenies, but not in fertilization rate （P〉0.05）, among the three groups. The hatching rate, survival rate and daily growth of the progeny of large-sized parents were greater than those of the control group （P〈0.05）, which in turn were larger than those of small-sized group （P〈0.05）. Responses to selection by shell length and body weight were 0.32±0.04 cm and 2.18±0.05 g, respectively, for the upward selection, and -0.14±0.03 cm and -2.77±0.06 g, respectively, for the downward selection. The realized heritability estimates of shell length and body weight were 0.38±0.06 cm and 0.22±0.07 g for the upward selection, and 0.24±0.06 cm and 0.37±0.09 g for the downward selection, respectively. The change in growth by bidirectional selection suggests that high genetic variation may be present in the cultured bay scallop population in China.

基于RAD-seq测序技术的墨西哥湾扇贝遗传改良后代及其双亲的遗传结构分析

本研究旨在阐明遗传改良后代墨西哥湾扇贝(Argopecten irradians concentricus)“橙黄1号”杂交选育系F5与其双亲的遗传关系及遗传进展。运用RAD-seq测序技术,对4个群体共96份扇贝样本进行了主成分分析(principal component analysis,PCA)、系统进化树构建及群体结构分析。进一步对墨西哥湾扇贝“橙黄1号”F5的30份样本进行亲本基因型转化及遗传多样性分析。结果表明,96份扇贝样本与参考基因组的平均比对率为96.45%,平均覆盖度为13.89%,平均覆盖深度为5.62×,共获得116533个高质量单核苷酸多态性(single nucleotide polymorphism,SNP)位点。群体遗传结构分析表明,96份扇贝样本被明显划分为4个类群,墨西哥湾扇贝“橙黄1号”F5的遗传结构与其双亲相近,介于双亲之间,与外群华贵栉孔扇贝(Chlamys nobilis)遗传结构相距较远。遗传多样性分析结果表明,墨西哥湾扇贝“橙黄1号”F5的平均观测杂合度为0.1485,低于平均期望杂合度0.3781。说明经过5代选育,墨西哥湾扇贝“橙黄1号”F5的遗传基因获得纯化。研究结果为墨西哥湾扇贝“橙黄1号”的遗传背景、亲缘关系及遗传进展提供依据。