北方沿海香港牡蛎(♀)×长牡蛎(♂)杂种中期优势评估

Analysis of the medium-term heterosis of Crassostrea hongkongensis( ♀) ×C. gigas(♂) hybrids in Northern China

为了评估香港牡蛎（♀）×长牡蛎（♂）杂种在北方沿海养殖中期能否产生种间杂种优势,在分析了早期杂种优势的基础上,以9个香港牡蛎自繁家系、9个长牡蛎自繁家系作为对照,以45个种间杂交家系为研究对象,进一步评估了中期杂种存活、生长及产量性状的杂种潜力及其优势。结果发现：1对于存活性状而言（360日龄）,香港牡蛎存活率较低仅为9.09%,死亡主要发生在越冬期间（90～180日龄）;长牡蛎存活率居中为51.26%,存活力下降主要原因是繁殖后夏季高温致死（360日龄）;而种间杂种的存活率相对较高为87.64%,表现出明显的存活优势,其杂种潜力hp=2.72,杂种优势H=189.88。2对于生长性状而言（360日龄）,从壳高水平上分析,长牡蛎平均壳高（50.74 mm）最大,显著大于香港牡蛎（45.17 mm）及杂交家系（42.70 mm）;且种间杂交家系壳高显著小于两亲本子代;其杂种潜力hp=-1.89,杂种优势H=-10.97。从鲜重上看,长牡蛎的鲜重（17.24 g）最大,显著大于香港牡蛎（12.58 g）及种间杂交家系（9.47 g）,且三者间彼此差异显著;其杂种潜力hp=-2.33,杂种优势H=-36.46。3对于产量而言,长牡蛎产量最高为3.22 kg,显著大于香港牡蛎（0.41 kg）,与杂交家系无显著差异（2.98 kg）;其杂种潜力hp=0.83,杂种优势H=63.97。研究表明,杂种在北方沿海养殖具有很好的抗低温、抗高盐能力,且存活力较强,但是生长性状表现出远交衰退特点。虽然产量性状具有杂种优势,略低于长牡蛎,但由于杂种外观上与香港牡蛎极其相似,故可以考虑将其作为北方牡蛎养殖的新品系（种）。同时,杂种在华南沿海是否具有杂种优势有待于进一步研究。

To improve the oyster phenotypic character,9 Crassostrea gigas families,9 C. hongkongensis families and 45 interspecific hybrid families were studied by the method of unbalanced nest design（ one male to three female） as subjects in July 2010. Moreover,their medium-term heterosis of hybrids including survival,growth and yield were examined in the identical conditions. These results show as follows：1Survival： The relative high survival rate（ 87. 64%） of hybrid was found with a significant survival advantage（ H = 189. 88）,while that of two parental fishes was lower than these of hybrids. Most of C.hongkongensis spat died during overwinter stage,and at the summer temperature was lethal for C. gigas spat.2Growth： The shell height of C. gigas maximum（ 50. 74 mm）,which was significantly greater than C.hongkongensis（ 45. 17 mm） and hybrid spats（ 42. 70 mm）; and that of hybrids was significantly less than the two parental progenies（ H =-10. 97）. Correspondingly,fresh weight of C. gigas（ 17. 24 g） maximum,which was significantly greater than C. hongkongensis（ 12. 58 g） and hybrid spats（ 9. 47 g）. These of hybrids were lighter than two parental species,and the heterosis was 36. 46. 3Yield： the yield of hybrids（ 2. 98 kg） was middle in that of C. gigas（ 3. 22 kg） and that of C. hongkongensis（ 0. 41 kg） with heterosis（ 63. 97%）. In conclusion,we found that hybrids retained the good low temperature resistance,high salt resistance and strong viability,but the growth outbreeding recession occurred in Northern China. Although the hybrid yield was slightly lower than that of C. gigas,hybrid oyster looked very similar to C. hongkongensis. It can be considered as a new line in northern oyster farming. Meanwhile,whether there is heterosis in Southern China needs further study.