长牡蛎中国群体和日本群体杂交子代的杂种优势分析

Heterosis of Hybrid Between Chinese and Japanese Populations of the Pacific Oyster(Crassostrea gigas)

为研究长牡蛎不同种群杂交的杂种优势,本研究选择长牡蛎中国群体（C）连续选育5代和日本群体（J）连续选育6代的个体作为亲本,进行完全双列杂交,比较分析了幼虫期、稚贝期和养成期3个阶段各实验组的生长与存活情况。研究表明：在幼虫期,杂交组的生长与存活性状表现出微弱的杂种优势,自交组JJ（J♀×J♂）和反交组JC（J♀×C♂）生长优势明显,而自交组CC（C♀×C♂）和正交组CJ（C♀×J♂）存活率较高,表明幼虫期存在显著的母性效应,正交组CJ存活率最高,杂种优势率为4.67%~40.30%。在稚贝期及养成期,杂交组各生长性状（壳高、壳长、壳宽和总重）表现出显著的杂种优势,总重的杂种优势率最高,为13.61%~21.71%,其中正交组CJ各生长性状的杂种优势率均表现为正值。从整个生长阶段来看,正交组CJ在幼虫期存活率最高,在稚贝期和养成期各生长性状均具有杂种优势,表明正交组CJ是最适的杂交组合,具有很大的生产潜力。

The Pacific oyster,Crassostrea gigas,which originated from Asia and was introduced to many countries,has had the highest production of any aquatic species for the past several years.Selection and cross-breeding programs for genetic improvement in C.gigas have initiated in several countries.In order to promote the development of cross-breeding,a complete diallel cross between Chinese and Japanese populations of the Pacific oyster（Crassostrea gigas）was carried out.With the increase in breeding algebra of the population,gene frequency differences between groups may be larger,hybrids may have a greater heterosis.In the study,Chinese population（C）was mass selected for five generations while Japanese population（J）was done so for six generation.Growth and survival performances were compared among hybrid and pure populations in different growth stages.Heterosis of growth traits was analyzed.The results indicated that the growth and survival of the two reciprocal crosses showed weak heterosis in larval stage.The pure bred group（JJ）and hybrid cross JC showed significant growth advantage,but pure bred group（CC）and the cross（CJ）lived well,indicating that there were significant maternal effects.Japanese population has been breeding more years,thus it may provide better growth vigor.But Chinese population has better adaptability in Chinese water,so it may provide better viability.In larval stage,the CJ cross had the highest survival rate with the heterosis ranging from 4.67% to 40.30%.In spat and adult stages,growth of the two reciprocal crosses showed heterosis comparable with the pure bred groups.Among the four traits（shell height,shell length,shell width and body weight）,2body weight had the highest heterosis,which varied between 13.61% and 21.71%.Besides,growth of the cross CJ showed positive heterosis in the whole spat and adult stages.In practice,besides the parent population,the selection of suitable parent combinations will take full advantage of heterosis.In a word,the results suggested that the CJ cross was the best with meaningful productive potential.When CC and JJ have been used as the core breeding populations,the cross C♀×J♂can stably improve growth and survival performance of C.gigas with the increase of selective breeding algebra.