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

Abstract

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 estimated 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, approximated 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.

Keywords

• Turbot
• Edwardsiella tarda
• Genetic parameter
• Ascites disease