Growth, survival and color segregation of F2 hybrids between selected “Haida no.1” and Orange-shell lines of the Pacific oyster

Abstract

In aquatic breeding work, much attention has been paid to the performance of the F1 hybrids. However, fewer studies have been conducted on the characteristics of F2 and Fn hybrids, especially in the intraspecific hybridization of the Pacific oyster Crassostrea gigas. In this study, the two purebreds, F1 hybrid families and F2 hybrid families was developed utilizing “Haida No.1” line (HH), Orange-shell line (OO) and their reciprocal hybrids (HO and OH) of C. gigas as the parents. The growth (shell height and wet weight), survival and shell color traits of the six groups were systematically investigated. Our results demonstrated the two F1 hybrid families exhibited significantly heterosis in shell height and wet weight compared to the purebred groups, with mid-parental heterosis at 9.85–36.49% and − 16.50–50.07%, respectively. Moreover, the traits of two F2 hybrid families were gradually inferior to F1 hybrid families from 6th month. Two F2 hybrid families exhibited inbreeding depression in wet weight compared to F1 hybrid families through the whole grow-out stage, with the values from −13.13% to −7.34%. However, the growth and survival advantages were existed in F2 hybrid families compared to their two parental counterparts. Meanwhile, the survival rate of the F2 hybrid families were greater than those of the parental groups during the grow-out stage, with superiority rate of 1.55–19.59%. Furthermore, some orange-shell and purple-shell individuals were detected in the F2 hybrid families. The rates of orange-shell individuals to non-orange shell individuals and purple-shell individuals to non-purple shell individuals were both 1:3. Surprisingly, the growth traits of orange-shell and purple-shell individuals in the F2 hybrid families were significantly superior than those of their corresponding controls (Orange-shell line and wild population). Through this comprehensively comparison analysis, we confirmed that F2 hybrids of C. gigas had obvious advantages in terms of shell height, wet weight and survival rate compared to the purebred lines, and the orange and purple individuals obtained from the F2 hybrid families have great potential to be used for the development for new strains.