太平洋牡蛎与近江牡蛎的种间杂交

为了评估太平洋牡蛎与近江牡蛎能否产生远缘杂种优势,于2010年5月,以成熟的两种牡蛎亲本为材料开展了2×2远缘杂交研究,由长牡蛎自繁组GG(Crassostrea gigas♀×C.gigas♂)、近江牡蛎自繁组AA(C.ariakensis♀×C.ariakensis♂)、正交组GA(Crassostreagigas♀×C.ariakensis♂)、反交组AG(C.ariakensis♀×C.gigas♂)4个实验组组成。分析了子代早期表型性状和杂种优势,并对杂交子代进行了遗传鉴定。结果表明:GA杂交组与AG组的受精强度具有不对称性。幼虫浮游期间,表型性状的中亲杂种优势几乎为0,GA组生长与存活性状表现出积极的单亲杂种优势,而AG组则具有明显的远交衰退现象;幼虫早期表型性状受到母本效应影响,而后减弱。变态期间,GA组变态率较高,得到了大量杂交稚贝;而AG组变态率极低,仅获得了72个杂交稚贝。稚贝培育期间,稚贝表现出中亲生长劣势与存活优势;GA组具有明显的单亲生长与存活优势,而AG组则表现出生长劣势并具有一定程度的存活优势。利用复合COI及ITS2鉴定了种间杂交子结果表明:正反交组杂交子均为真正意义上的两性融合杂交子。实验获得了具有显著杂种优势的GA组杂交子,为现有牡蛎的遗传改良提供了新的方向。

Interspecific hybridization between two oysters Crassostrea gigas and C. ariakensis

To evaluate whether heterosis can be obtained from hybridization between Crassostrea gigas and C. ariakensis, a 2×2 factorial cross experiment was conducted between these two species in May 2010. Heterosis was first examined by comparing growth and survival of the two reciprocal hybrid crosses (GA and AG) with that of the two parental crosses (GG and AA). Gametic compatibility between the two species was asymmetric with GA crosses having higher fertilization success than AG crosses. In the hybrid crosses, GA offspring were significantly larger than AG offspring. Larval growth of interspecific crosses was similar to that of the maternal species during the first nine days, indicating dominant maternal effects. Beyond larval day 9, however, we observed asymmetry in single parent heterosis for growth and survival for both larvae and spat. GA crosses had good success in metamorphosis, while AG crosses produced only 72 spat. Heterosis was positive for GA hybrids but negative for AG hybrids, with the exception of higher AG survival during the grow-out stage. Maternal origin had a dominant effect on heterosis of both growth and survival, while the interaction between maternal origin and mating type was the second significant factor impacting growth heterosis during the first several days. After that, mating type emerged as an independent factor influencing growth heterosis for the rest of the larval stage. Genetic analysis confirmed that the spat of reciprocal crosses contained DNA from both species. Our study indicates that interspecific hybridization between female C. gigas and male C. ariakensis may be a promising method for genetic improvement of these two species for aquaculture.