title: Rainbow trout (Oncorhynchus mykiss) resistance to columnaris disease is heritable and favorably correlated with bacterial cold water disease resistance.
abstract: Columnaris disease (CD), caused by Flavobacterium columnare, is an emerging disease affecting rainbow trout aquaculture. Objectives of this study were to 1) estimate heritability of CD resistance in a rainbow trout line (ARS-Fp-R) previously selected 4 generations for improved bacterial cold water disease (BCWD) resistance; 2) estimate genetic correlations among CD resistance, BCWD resistance, and growth to market BW; and 3) compare CD resistance among the ARS-Fp-R, ARS-Fp-S (selected 1 generation for increased BCWD susceptibility), and ARS-Fp-C (selection control) lines. Heritability of CD resistance was estimated using data from a waterborne challenge of 44 full-sib ARS-Fp-R families produced using a paternal half-sib mating design, and genetic correlations were estimated using these data and 5 generations of BCWD resistance, 9-mo BW (approximately 0.5 kg), and 12-mo BW (approximately 1.0 kg) data from 405 ARS-Fp-R full-sib families. The CD and BCWD challenges were initiated at approximately 52 and 84 d posthatch, or approximately 650 and 1,050 degree days (°C × d), respectively. Survival of ARS-Fp-R families ranged from 0 to 48% following CD challenge and heritability estimates were similar between CD (0.17 ± 0.09) and BCWD (0.18 ± 0.03) resistance, and the genetic correlation between these 2 traits was favorable (0.35 ± 0.25). Genetic correlations were small and antagonistic (-0.15 ± 0.08 to -0.19 ± 0.24) between the 2 resistance traits and 9- and 12-mo BW. Two challenges were conducted in consecutive years to compare CD resistance among ARS-Fp-R, ARS-Fp-C, and ARS-Fp-S families. In the first challenge, ARS-Fp-R families (83% survival) had greater CD resistance than ARS-Fp-C (73.5%; P = 0.02) and ARS-Fp-S (68%; P < 0.001) families, which did not differ (P = 0.16). In the second challenge, using an approximately 2.5-fold greater challenge dose, ARS-Fp-R families exhibited greater CD resistance (56% survival) than ARS-Fp-S (38% survival; P = 0.02) families. The favorable genetic correlation between CD and BCWD resistance is supported by greater CD resistance of the ARS-Fp-R line compared to the ARS-Fp-C and ARS-Fp-S lines and suggests that both traits will be improved simultaneously when selection is practiced on only 1 trait. In summary, these data indicate the feasibility of further selective breeding of the BCWD-resistant ARS-Fp-R line for increased CD resistance to produce a double pathogen-resistant line of rainbow trout.
authors.forename: J P
authors.initials: JP
authors.lastname: Evenhuis
authors.forename: T D
authors.initials: TD
authors.lastname: Leeds
authors.forename: D P
authors.initials: DP
authors.lastname: Marancik
authors.forename: S E
authors.initials: SE
authors.lastname: LaPatra
authors.forename: G D
authors.initials: GD
authors.lastname: Wiens
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods; D003080:Cold Temperature; D060467:Disease Resistance / Q000235:genetics* / Q000502:physiology; D004198:Disease Susceptibility / Q000503:physiopathology / Q000662:veterinary; D005260:Female; D005393:Fish Diseases / Q000235:genetics* / Q000503:physiopathology; D045826:Flavobacteriaceae Infections / Q000235:genetics / Q000503:physiopathology / Q000662:veterinary*; D005417:Flavobacterium / Q000502:physiology; D020022:Genetic Predisposition to Disease / Q000235:genetics; D007178:Inbreeding; D053208:Kaplan-Meier Estimate; D008297:Male; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000382:microbiology* / Q000502:physiology; D010641:Phenotype