Identification of candidate DNA markers associated with IHN virus resistance in backcrosses of rainbow (Oncorhynchus mykiss) and cutthroat trout (O-clarki)

Infectious hematopoietic necrosis (IHN) is a rhabdoviral disease of salmoni d species. Initial observations suggested that cutthroat trout (Oncorhynchu s clarki) and hybrids of rainbow trout (Oncorhynchus mykiss) and cutthroat trout are significantly less susceptible to IHN virus (IHNV) than rainbow t rout. Sixteen full-sib families of backcross progeny (female rainbow X male hybrid) were produced and three replicates per family were challenged with IHNV. DNA fingerprints of mixtures from first mortalities and survivors of the IHNV challenges were compared using two restriction enzymes and 10 mul tilocus probes. An estimated 98-102 polymorphic loci were screened by the b ulked segregant analysis (BSA) of the DNA mixtures. Thirty-three multilocus RFLP markers differing between first mortalities and survivors were detect ed. Of 17 tested a significantly higher frequency of two markers was detect ed among individuals first to die in one family (C2), and another marker wa s significantly associated with IHNV resistance in family A4. (C) 1999 Else vier Science B.V. All rights reserved.