Estimates of genetic parameters and genotype by environment interactions for growth traits of rainbow trout (Oncorhynchus mykiss) as inferred using molecular pedigrees

Genetic correlations between three character sets (early progeny growth; later progeny growth at 8.5 degreesC; later progeny growth at 15 degreesC) were determined from within the scope of a working commercial rainbow trout (Oncorhynchus mykiss) aquaculture facility. Micrasatellite multiplex genotyping systems were used to resolve the molecular pedigrees for groups of progeny with high accuracy (91-95%). The heritability estimates obtained from restricted maximum likelihood (REML) were higher than expected, ranging from 0.360 to 0.719 for the growth traits total length, weight and condition factor. Estimates of genetic correlations were obtained through correlation of single trait estimated breeding values (EBV), correlation of multiple trait EBV, and by estimates of genetic correlations coming directly from multiple trait REML. REML determined genetic correlations were high (0.86 +/- 0.026), indicating that early progeny growth is a good predictor of later progeny growth and that the magnitude of genotype by environment interactions (G x E) is low. Genetic correlations estimated from multiple trait EBV (0.84 +/- 0.048) were not significantly different from the REML estimates. Both were significantly different from the genetic correlations estimated from single trait EBV (0.60 +/- 0.049), suggesting that single trait estimates have limited value. Interestingly, the genetic correlations between condition factor and length or weight of all character sets were significantly different from unity, indicating that condition factor is a trait that is genetically independent of both length and weight. (C) 2000 Elsevier Science B.V. All rights reserved.