The diallel cross of Manila clam (Ruditapes philippinarum) populations from Fujian and Guangdong Provinces

In 2015, from Septemper to December, a diallel cross was conducted using two populations of Manila clam Ruditapes philippenarum from cultured Fujian stock and wild Guangdong stock which was F₁ progeny. The growth, survival rate and heterosis at larval and juvenile periods were compared among the two reciprocal hybrid crosses and two parental crosses. The results indicated that all the four experimental groups had high fertilization and hatching rates, and did not show significant difference between each other. Totally, at larval period, maternal origin had significant effect on growth. While mating strategy was the major factor for growth hybrid effect during juvenile. In contrast, at larval period, mating strategy had significant effect on survival, while maternal origin was the major factor for survival during juvenile. This showed that gamete incompatibility and embryonic development disorders did not exist in interspecific hybridization between different geographical populations of R. philippenarum. At larval period, no growth or survival heteiosis was observed between two hybrid crosses and the two parental groups. In contrast, at juvenile period, the growth performances of two hybrid crosses were superior to the two parental groups, showing heteiosis in the characteristics of shell height and shell length after 30 days of age. Especially, at 40 days of age, heterosis values of shell height and shell length reached maximum, which were 25.64 and 27.00, respectively. This perhaps attributed to development difference of expression of heterosis. For survival rate, at larval period, the Fujian parental cross had the best performance which was 36.45%±1.85%. And the juvenile survival rate of the Guangdong parental cross was 52.27%±2.13%, which was higher than other three experimental crosses. In total, survival heterosis was not observed during the study. This was attributed to the fact that survival-related gene frequency of two geographic parental populations had no difference or detection was less often.