Analysis of a diallel cross to estimate effects of crossing on resistance to enteric septicemia in channel catfish, Ictalurus punctatus

Abstract

The trend in commercial channel catfish, Ictalurus punctatus, production is toward increased stocking densities and feeding rates, and is often accompanied by disease problems. Enteric septicemia, caused by the bacterium, Edwardsiella ictaluri, is responsible for many disease losses in channel catfish cultured in the southern United States. A complete diallel cross among three strains, Red River, Norris, and M X K (Marion X Kansas), was used to estimate effects of crossing on resistance to E. ictaluri. Juveniles (mean weight 15.2 ± 3.8 grams) from all nine crosses were challenged by immersion, and survival determined 28 days following bacterial exposure. Mean survival of all crosses was 62.2% and ranged from 35.8% in the M X K female X Norris male cross to 90.0% in the Norris female X M X K male cross. Estimates for heterosis, line, maternal, reciprocal effects, and general combining ability corrected for maternal effects were obtained from contrasts among appropriate mean squares. Average, line or specific heterosis effects were not significant suggesting that crossbreeding these strains would not increase disease resistance due to heterosis. Significant line effects in Norris and M X K strains demonstrated differences for disease resistance in these strains. Significant maternal effects conveyed increased disease resistance to offspring in the Norris strain. Significant general combining ability indicated additive genetic differences for enteric septicemia resistance in Norris and M X K strains.