GENETICS OF RESISTANCE TO DISEASE IN FISHES

The first part of this paper deals with the identification and exploitation of genetic variations in resistance to diseases. At the interspecific level, hybridization may in some cases allow the exploitation of the character of resistance of one of the parents. Polyploid hybrids represent a particular advantage for this approach. Variations between populations have been treated in many papers. However, the studies are generally limited to F1 crosses and do not allow analysis of genetic determinism of the observed variations. Significant variations are also observed between individuals of one and the same population. Several mass selection results using this variability have been developed. The second part deals with disease resistance mechanisms. At the quantitative level, the studies concern the variability of antibody levels, neutralizing serum and mucus activities and resistance to stress; several cases of correlation between these characters and resistance to diseases are presented. The Mendelian approach is particularly developed in the field of histocompatibility genetics. However, the link between this variability and disease resistance remains to be established. The final discussion deals with the respective advantages of quantitative, Mendelian and molecular biology approaches in order to improve disease resistance in fish. © 1990.