Crossbreeding of two populations of Ruditapes philippenarum reveals high growth and survival heterosis

Abstract

Hybridization is an important breeding method to improve productive traits in aquaculture. The Manila clam Ruditapes philippenarum, a worldwide cultured bivalve, has achieved the great commercial success owing to a global appreciation of its delicious taste and affordable price. In order to evaluate the aquaculture potential of clam hybridization, a complete diallel cross between two geographical populations (Shandong and Guangdong) was performed in the present study. Two intra-population mating groups LL (L♀ × L♂) and ZZ (Z♀ × Z♂) and two crossbreeding groups ZL (Z♀ × L♂) and LZ (L♀ × Z♂) were established to investigate the potential heterosis of growth and survival in the clams. Three full-sib families were constructed in each mating group to calculate the growth and survival heterosis. During the larval stage (2 ∼ 10d), no significant difference was detected in averaged shell length between reciprocal hybrids and inbred groups. In contrast, hybrid spats after 15d cultivation showed a significantly larger size (shell length and shell height) than that of inbred spats. For the reciprocal hybrids, the greatest growth heterosis of shell length and height (33.42% and 33.13%) was detected from 20 days after fertilization in ZL. After 40d cultivation, ZL displayed the most growth potential in shell length and height, reaching maximum values of 0.900 and 0.858 mm, respectively. The hybrids had 25% ∼ 40% higher survival rates than those of the inbred groups, with the highest survival heterosis in ZL. The positive values for the general combining ability (GCA) were consistently detected in the Zhanjiang population. At day 40, the special combining ability (SCA) in ZL was approximately two-fold higher than that in LZ. These findings indicate that the hybrids produced by Laizhou males and Zhanjiang females have the greater aquaculture potential, providing a useful crossbreeding strategy for clam genetic improvement in aquaculture.