Assessment of genetic variability among strains of rainbow and cutthroat trout using multilocus DNA fingerprints

Abstract

DNA fingerprint banding patterns of mixed DNA samples from 17 to 28 individuals from five strains of rainbow trout ( Oncorhynchus mykiss) and two strains of cutthroat trout ( Oncorhynchus clarki) were analyzed to quantify genetic differences among the seven populations. Levels of within-population genetic variability were estimated by comparing DNA fingerprint banding patterns of individuals. Three multilocus oligonucleotide probes were used to detect the DNA fingerprints of individuals and mixtures. Scanning image analysis and customized software programs were used to assign band identity and to determine the degree of band-sharing between and within populations. The distinct genetic differences we identified between the Yellowstone cutthroat ( O. c. bouvieri) strain and the westslope cutthroat ( O. c. lewisi) strain, and between the two cutthroat subspecies and the five rainbow trout strains, are consistent with previous studies. Lower genetic variabilities were observed within the cutthroat trout strains, which is consistent with their previously reported lower heterozygosities at protein loci. Varying levels of genetic variability were identified within the rainbow trout strains, and the low level of variability detected among individuals from one of the strains is probably associated with previously observed symptoms of inbreeding depression in that strain. Our results suggest that multilocus DNA markers can be best utilized in studies of genetic variability among closely related populations and in breeding programs.