Estimation of genetic parameters of growth traits and genetic gain of F5 generation of scallop Hongmo No. 1

Argopecten irradians concentricus, natively distributed along the Atlantic coast of the United States, has advantages of fast growth, short growth cycle, and high meat yield. It was introduced into China mainland in 1991 and in 2001 its large-scale aquaculture began in the Beibu Gulf area. More than 20 years since the introduction of A. irradians concentricus, as the number of breeding generations increased, the characteristics of the breeding population deteriorated seriously reflected in small individuals, low survival rates, and low meat yields. To solve the problem of germplasm degradation of A. irradians concentricus, this research team hybridized A. irradians concentricus with the scallop Bohai Red in 2016, and successfully obtained hybrid offspring. After four generations of breeding, a new strain of scallop Hongmo No. 1 was obtained. Hongmo No. 1 has the characteristics of a fast growth rate, high survival rate, and high temperature resistance, and has completely adapted to the environment of Beibu Gulf in the south of China, so it has a good prospect of popularization and breeding. Although Hongmo No. 1 has been bred for multiple generations, the genetic parameters of its growth-related traits are unknown and whether it still has breeding potential is unclear. As a result of successive selection in a closed population, genetic parameters varied between different generations of selected strains. Obtaining estimates of genetic parameters and genetic gain of growth-related traits of scallop Hongmo No. 1, which has experienced numerous generations of selection, is of great significance for subsequent breeding. To evaluate the breeding effect of the new scallop strain Hongmo No. 1, this study compared the selected line and a non-selected line in the F4 generation of Hongmo No. 1 and evaluated the genetic parameters and genetic gain of F5 growth-related traits. The results indicated that in the F5 generation of Hongmo No. 1 there was no significant difference in the survival rate between the selected line and the non-selected line (P>0.05), but the growth traits of the selected line were significantly better than those of the non-selected line (P<0.05). The coefficients of variation of quality traits of the two populations of Hongmo No. 1 F5 were 14.60%-28.30%, showing potential for successive selective breeding. The genetic gain of shell length, shell height, shell width, body weight, adductor muscle weight, soft tissue weight, and shell weight in the F5 generation were 7.25%, 7.13%, 4.86%, 25.42%, 31.60%, 27.70%, and 21.29%, respectively. The realized heritability of shell length, shell height, shell width, body weight, adductor muscle weight, soft tissue weight, and shell weight in the F5 generation were 0.37, 0.36, 0.25, 0.36, 0.32, 0.38, and 0.32, respectively, which are moderate levels of heritability. The results of this study showed that the growth traits of the selected line were better than those of the non-selected line, both of which showed a large coefficient of variation for quality traits, moderate mean genetic gain, and medium realized heritability. These results indicate that the genetic improvement of A. irradians concentricus, using first hybridization and then sub-breeding, has achieved good results. These results provide a basis for further breeding of growth traits in scallop Hongmo No. 1