ARS | Publication request: HETEROSIS AND GENETIC DISTANCE IN STRAIN CROSSES OF RAINBOW TROUT

Submitted to: Aquaculture America Conference
Publication Type: Abstract
Publication Acceptance Date: October 15, 2004
Publication Date: January 10, 2005
Citation: Silverstein, J., Parsons, J., Rexroad III, C.E., Palti, Y. 2005. Heterosis and genetic distance in strain crosses of rainbow trout. Aquaculture America Conference 2005. New Orleans, LA 1/17 - 1/20/2005.

Technical Abstract: A breeding program to develop rainbow trout with improved performance for the US rainbow trout aquaculture industry is being conducted at the National Center for Cool and Cold Water Aquaculture (NCCCWA). To establish a broad genetic base, genetic material has been incorporated from six unrelated populations. The aim of this study is to evaluate the potential for using outcrossing as a strategy to improve performance in rainbow trout. Crosses within and among rainbow trout from four different populations were produced over the 2002 and 2003 broodyears. Heterosis, or the performance advantage of offspring from outcrossed parents, is dependent on genetic differences in parents that result in increased heterozygosity of offspring (overdominance). Greater differences (greater genetic distance) between populations may result in offspring with performance advantages due to heterosis. Microsatellite markers for 9 polymorphic loci were used to characterize the populations used at NCCCWA and the degree of genetic differentiation (FST) between populations. Larger FST values indicate greater differentiation. For rainbow trout populations over a large geographic range, FST values typically range from 8 to 15%. The four populations considered here were all distinct and the pairwise FST values ranged from 7.2 to 10.7%. Since growth is the primary trait of interest, weight at 270 days was used to evaluate growth. Percent heterosis (% heterosis) calculations ranged from as high as 15.8% to 1.4% and showed that there may be some gain in size attributable to heterotic effects, however the best within strain cross performed better than any outcross. There was no correlation between FST and %heterosis for growth (N=6, r<0.2, P>0.6). The data describing heterotic effects on feed intake are being analyzed. The potential for gains due to outcrossing must be weighed against the costs of maintaining multiple distinct populations.