Genetic effects of ELISA-based segregation for control of bacterial kidney disease in Chinook salmon (Oncorhynchus tshawytscha)

We evaluated genetic variation in ability of Chinook salmon (Oncorhynchus tshawytscha) to resist two bacte- rial pathogens: Renibacterium salmoninarum, the agent of bacterial kidney disease (BKD), and Listonella anguillarum, an agent of vibriosis. After measuring R. salmoninarum antigen in 499 adults by enzyme-linked immunosorbent assay (ELISA), we mated each of 12 males with high or low antigen levels to two females with low to moderate levels and exposed subsets of their progeny to each pathogen separately. We found no correlation between R. salmoninarum anti- gen level in parents and survival of their progeny following pathogen exposure. We estimated high heritability for re- sistance to R. salmoninarum (survival h 2 = 0.890 ± 0.256 (mean ± standard error)) independent of parental antigen level, but low heritability for resistance to L. anguillarum (h 2 = 0.128 ± 0.078). The genetic correlation between these survivals (rA = -0.204 ± 0.309) was near zero. The genetic and phenotypic correlations between survival and antigen levels among surviving progeny exposed to R. salmoninarum were both negative (rA = -0.716 ± 0.140; rP = -0.378 ± 0.041), indicating that variation in antigen level is linked to survival. These results suggest that selective culling of female broodstock with high antigen titers, which is effective in controlling BKD in salmon hatcheries, will not affect resistance of their progeny.