Crossbreeding of three selected strains of Crassostrea gigas reveals heterosis in survival and growth

Genetic improvement via crossbreeding has been widely used in aquaculture production. In this study, we conducted intraspecific hybridization using three consecutive generation selected strains of Crassostrea gigas from China (C), Japan (J), and South Korea (K). Six hybrid lines and three purebred lines were constructed and their growth and survival rates were recorded to evaluate the heterosis and combining ability. The crosses of CJ (C♀ × J♂) and CK (C♀ × K♂) displayed higher heterosis for survival and growth during the larval to the adult stage. Specifically, the survival and growth rates of CK improved by 45.41% and 13.97%, respectively, compared to the KK group. At the grow-out stage, the survival rate and shell height of CJ were 34.23% and 15.87% higher than the JJ group. The general combining ability (GCA) of strain C was consistently positive at various ages, ranging from 1.36 to 4.68. The special combining ability (SCA) of the six hybrid combinations varied with age, yet the CJ and CK cross consistently maintained positive SCA values. These results indicate that strain C is a superior parental line and that CJ and CK represent optimal hybrid combinations. By crossing selected oyster lines, hybrids with enhanced survival and growth performance can be produced.