Disease resistance of carp, Cyprinus carpio L.: identification of individual genetic differences by bath challenge with atypical Aeromonas salmonicida

The present study was undertaken to identify female breeders, resistant or susceptible to disease, which might be used to obtain gynogenetically cloned carp lines differing in disease resistance. Experimentally induced erythrodermatitis was used as the disease model. Firstly, the effect of age on the resistance to bath challenge with atypical Aeromonas salmonicida was examined. These challenges indicated a shift from subacute to chronic infection with increasing age, as shown by a lower survival at 3 and 5 months (both 15%) compared to 10 months of age (60%). Then, to conserve and characterize breeder females, offspring of two females (nos 21 and 38), including F1, F2 and backcross (B1 and B2) progenies, were bath challenged at the age of 3 months. Comparison of the survival data showed a segregation into two groups of progenies: one resistant with nearly 100% survivors (W, F1 and B2), and one relatively susceptible group with 25% (R8 and F2) or 50% (B1) mortality. Analysis of inheritance indicated dominance of the resistant phenotype. Thus, the results identified two breeder females whose (gynogenetic) progeny might be expected to differ in resistance to bath challenge with atypical A. salmonicida.