Genetic markers associated with resistance to infectious hematopoietic necrosis in rainbow and steelhead trout (Oncorhynchus mykiss) backcrosses

Backcrosses of rainbow trout and steelhead (Oncorhynchus mykiss) were used to construct a linkage map and to identify associations between molecular markers and quantitative trait loci (QTL) determining resistance to infectious hematopoietic necrosis virus (IHNV). The sire map covers 1019 centimorgans (cM), and it is composed of 257 molecular markers [185 amplified fragment length polymorphisms (AFLPs) and 72 microsatellites] distributed over 28 linkage groups. The dam map consists of 236 markers (164 AFLPs and 72 microsatellites), with a total of 45 linkage groups, covering 2041 cM. Sixty-one new microsatellite markers were added to the existing rainbow trout linkage maps. Six AFLPs and six microsatellites in the dam map were associated with IHNV resistance and were located in linkage groups 3, 14, 16, 30, 31, and 39. Sixteen AFLPs and six microsatellites associated with IHNV resistance were located in linkage groups 11, 20, and 25 in the sire map. Microsatellite markers mapped to the three linkage groups were used to screen nine other families, and QTL-marker associations were observed for four of the markers in at least one of the families. Further marker mapping is required to increase resolution and to ultimately facilitate positional cloning of QTLs affecting IHNV resistance.