Estimating genetic parameters of resistance against Edwardsiella tarda in turbot (Scophthalmus maximus)

Ascites disease, caused by Edwardsiella tarda, is one of the most destructive diseases in turbot (Scophthalmus maximus). Genetic improvement of host germplasm aiming at resistance to E. tarda is the fundamental way to control this disease. However, genetic parameters for this trait in turbot are so far completely unknown, which are necessary for designing breeding protocols. In the current study, genetic parameters of this trait were esti-mated based on phenotype data collected using infection artificially. Challenge test survival was defined using three different trait definitions: Survival days after infection (SD), survival status at the half lethal time (SS50), test-day survival (TDS), and each trait definition was analyzed using appropriate models. In the challenge test, all the fish died from 6 to 14 days post infection. The heritability for SD and SS50 based on animal model were 0.43 +/- 0.11 and 0.24 +/- 0.07. When sire-dam model was used, all the heritability estimates were consistent and high, ranged from 0.72 to 0.76. Genetic correlation between resistance to E. tarda and harvest body weight, approx-imated by Pearson correlations between their average family estimated breeding values (EBVs), ranged from 0.14 to 0.45. These results indicated that selective breeding for resistance to E. tarda can be successfully applied in the breeding population.

Automated summary

This study aimed to determine the genetic parameters for the resistance of turbot to Edwardsiella tarda in order to design breeding protocols. The results showed consistent and high heritability estimates in the sire-dam model, indicating the successful application of selective breeding for resistance to E. tarda in the breeding population.