Heterosis and combining ability： a diallel cross of three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino

We conducted a complete diallel cross among three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino to determine the heterosis and the combining ability of growth traits at the spat stage. The three populations were collected from Qingdao （Q） and Dalian （D） in China, and Miyagi （M） in Japan. We measured the shell length, shell width, and total weight. The magnitude of the general combining ability （GCA） variance was more pronounced than the specific combining ability （SCA） variance, which is evidenced by both the ratio of the genetic component in total variation and the GCA/SCA values. The component variances of GCA and SCA were significant for all three traits （P〈0.05）, indicating the importance of additive and non-additive genetic effects in determining the expression of these traits. The reciprocal maternal effects （RE） were also significant for these traits （P〈0.05）. Our results suggest that population D was the best general combiner in breeding programs to improve growth traits. The DM cross had the highest heterosis values for all three traits.