Premium
Genetic Variation in Resistance to the Hemoflagellate Cryptobia salmositica in Coho and Sockeye Salmon
Author(s) -
Bower S. M.,
Withler R. E.,
Riddell B. E.
Publication year - 1995
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/1548-8667(1995)007<0185:gvirtt>2.3.co;2
Subject(s) - biology , enzootic , intraspecific competition , oncorhynchus , zoology , genetic variation , strain (injury) , virulence , parasite hosting , fishery , virology , fish <actinopterygii> , genetics , virus , gene , anatomy , world wide web , computer science
Intra‐ and intraspecific differences in genetic variation for resistance to the pathogenic hemoflagellate Cryptobia salmositica were identified in coho salmon Oncorhynchus kisutch and sockeye salmon O. nerka . For each species, a strain sampled from a location enzootic to C. salmositica was more resistant than one sampled from outside the enzootic area. In coho salmon inoculated with 10‐fold serial dilutions of 10 6 to 10 2 C. salmositica , survival was 95% in the resistant strain, 3% in the susceptible strain, and intermediate (30%) in the intraspecific hybrid strains. Genetic variation for survival detected in the hybrids was attributable to the susceptible strain only, indicative of strong selection pressure imposed on the fish by the parasite. For sockeye salmon treated identically, survival was 90% in the resistant, 40% in the susceptible, and 70% in the hybrid strains. Survival in both purebred sockeye salmon strains displayed additive and nonadditive genetic variation. Survival of intraspecific hybrid coho salmon decreased with increasing inoculation level; this effect was less marked in the susceptible and absent from the resistant sockeye salmon strains. There was significant genetic variation for time to death within the sockeye but not coho salmon strains. Differences in genetic variation for resistance in coho and sockeye salmon may arise from differences in the resistance mechanisms, the selection pressure applied to each species, the genetic control of resistance, or some combination of these factors. Differences in resistance were not caused by the parasite because its virulence was consistently high.