Novel insights into the selective breeding for disease resistance to vibriosis by using natural outbreak survival data in Chinese tongue sole (Cynoglossus semilaevis)

As an important farmed flatfish species, Chinese tongue sole (Cynoglossus semilaevis) is heavily threatened by vibriosis in recent years. Genetic selection for disease resistance is a sustainable and effective approach to reduce frequent outbreaks. To verify whether the resistance of vibriosis (caused by co-infections of different Vibrio spp. in natural outbreak) can be included in breeding programs, in this study, genetic analysis of resistance to vibriosis based on natural outbreak survival data was carried out by using four statistical models (three cross-sectional models and one longitudinal model). The magnitude of the genetic variation in the resistance of vibriosis was estimated through a 56-day natural outbreak test of 15,912 individuals from 78 full-sib families (the offspring of 77 sires and 78 dams). Variance components and heritabilities were estimated at two cut-off points respectively, i.e. day 35 with 49.2% cumulative mortality and day 56 with 71.6% finial cumulative mortality. Heritabilities of resistance to vibriosis were low to moderate, where values at day 56 (0.04-0.21) were significantly different from zero, while values at day 35 (0.03-0.10) were not significantly different from zero in each corresponding model. The Spearman rank correlations between family EBVs for different models were high (> 0.98), indicating a nearly identical ranking of families. Compare to three simpler cross-section models, the longitudinal model taken the time until death into account demonstrated the highest accuracy of family selection. These results confirmed the existence of genetic variation for resistance to vibriosis and provided novel insights into the selective breeding for disease resistance to vibriosis by using natural outbreak survival data in tongue sole.