|dc.description.abstract||Eleven genetic types, Kansas Random × Rio Grande, Kansas Select × Rio Grande, 103KS × Rio Grande, Marion Select × Rio Grande, 103 KS × B, Marion Select × B, Auburn-Rio Grande × B, 103KS × D&B, Kansas Random × D&B, Marion Random × D&B, and Kansas Select × D&B, of channel catfish, Ictalurus punctatus, female × blue catfish, I.furcatus, male hybrid catfish were challenged with virulent Flavobacterium columnare in tanks. Sex and the interaction between sex and genotype did not affect the disease resistance. The genetic type was the key factor associated with columnaris resistance of hybrid catfish. There was no apparent sire effect, but there was a significant (P<0.05) dam effect on mortality, median death time and average survival times. 103KS had the best combining ability to produce hybrids with the best columnaris resistance. The best strategy to improve disease resistance of hybrid catfish is to identify female strains with the best combining ability. Potential genetics of these dam effects requires further study.
Two genetic types of hybrids and one genetic type of channel catfish performed similarly in regards to mortality and survival time when challenged with Edwardsiella ictaluri, causative agent of enteric septicemia of catfish (ESC). However, the channel catfish had the largest death rate. The experiment was complicated by co-infections with both ESC and Ichthyophthirius multifiliis (Ich). The mortality and survival time of the two types of ich infected hybrid catfish were similar, while the death rate and extent of death for the channel catfish were the highest. The difference in ESC resistance of the hybrid catfish and channel catfish were not as great as seen in earlier experiments. This may be a result of genotype-environment interactions from the intensity of the infection or the multiple infections. Additionally, the channel catfish used in this study was an intraspecific crossbred in channel catfish and may have improved disease resistance compared to channel catfish in previous comparisons. Intraspecific crossbreeding may be an alternative to interspecific hybridization for enhancement of disease resistance and should be further explored.||en_US