Genetics and genomics - integration of molecular genetics into a breeding program for rainbow trout

Abstract

At the National Center for Cool and Cold Water Aquaculture (US Department of Agriculture, Ag. Research Service) in Leetown, WV, we have a broodstock development program now entering the second generation of family-based selective breeding using expected breeding values (EBVs). Our major breeding objectives are faster growth and resistance to Flavobacterium psy- chrophilum, the causative agent of bacterial coldwater disease. For these traits we have devel- oped assays to evaluate phenotypic performance. In addition to our breeding program, we are participating in an international collaboration to develop a microsatellite marker linkage map for the rainbow trout with the intent of identifying quantitative trait loci (QTL) and using them in mark- er (MAS) or gene-assisted (GAS) selection. There are several possible approaches with regard to the types and numbers of markers to develop and the strategies and methods for implement- ing the markers in a selective breeding program. This paper describes the choices we made con- cerning QTL identification for traits of high, low, and unknown degrees of heritability. These traits are plasma cortisol response to a crowding stress (h2 = 0.4), feed intake (h2 = 0.1) and resis- tance to F. psychrophilum (0.3