Heritability of resistance to viral nervous necrosis in Atlantic cod ( Gadus morhua L .)

Abstract

Nodavirus are the causative agents of viral nervous necrosis (VNN), and has been shown to cause mortality in numerous fish species worldwide, among them is the Atlantic cod ( Gadus morhua L .). In this study, heritability of VNN resistance in Atlantic cod was estimated through challenge testing of 50 large full sib families (∼ 94 fish per family) comprising two genetically distinct groups of Atlantic cod (Norwegian coastal cod and northeast Arctic cod) and their F1 crossbreds. The overall survival (dead/alive) at end of test was 30%, but coastal cod had considerably higher survival (56%) than northeast Arctic cod (10%), while the F 1 cross was intermediate (31%). Furthermore, enormous variation in family survival was observed within each group (17 to 82% for coastal cod, 0 to 42% for northeast Arctic cod and 0 to 92% for the F 1 cross). As a consequence, the estimated within-strain heritability of survival under challenge testing was extremely high (0.75 ± 0.11 on the underlying scale and 0.43 ± 0.07 on the observable scale). Common environmental effects of full-sib families were not significant in addition to additive genetic effects, but the data structure was not optimal for distinguishing these effects.