Inter-strain differences in the association between mitochondrial DNA haplotype and growth in cultured Ontario rainbow trout (Oncorhynchus mykiss)

We reared progeny groups of rainbow trout (Oncorhynchus mykiss) from two aq uaculture strains in a controlled laboratory experiment to test if fish wit h different mtDNA haplotypes show variation in body weight and growth. The ova from 12-13 females were each combined with milt from two males in singl e-pair matings to produce a set of half-sib families for each strain. Sprin g Valley progeny from different males varied in wet weight at 210 and 293 d ays post-fertilization but not weight-specific growth rate (WGR). The proge ny of different males from the Rainbow Springs strain varied significantly in both wet weight on each sampling day and WGR. Fish with different mtDNA haplotypes (Spring Valley: comparison of haplotypes 1, 10, 13; Rainbow Spri ngs: 9, 10, 13) varied significantly in wet weight (Spring Valley) and WGR (both strains). The relative performance of fish with specific haplotypes w as consistent across males within strains but not across strains. For examp le, haplotype 10 fish had significantly lower WGR than haplotype 13 fish in Rainbow Springs but did not differ significantly in Spring Valley, This su ggests that marker-assisted selection (MAS) based on mtDNA haplotypes must proceed with caution in Ontario rainbow trout. (C) 1999 Elsevier Science B. V. All rights reserved.