Plant & Animal Genome VI Conference

P343

A TEST FOR ASSOCIATION BETWEEN MHC POLYMORPHISMS AND IHN VIRUS RESISTANCE IN BACKCROSSES OF RAINBOW AND CUTTHROAT TROUT

1. Department of genetics and Cell Biology, Washington State University, Pullman, WA 99164-4234, USA
2. Department of Zoology, Washington State University, Pullman, WA 99164-4236, USA
3. Blue Lakes Trout Farm, Inc., P.O. Box 1237, Twin Falls, ID 83303, USA

Infectious hematopoietic necrosis (IHN) is a rhabdoviral disease of salmonid species. Initial observations suggested that cutthroat trout (Oncorhynchus clarki) and hybrids of rainbow trout (Oncorhynchus mykiss) and cutthroat trout are significantly less susceptible to IHN virus (IHNV) infection than rainbow trout. We previously applied multilocus RFLP fingerprinting to identify DNA markers linked to IHNV resistance. Sixteen full-sib families of backross progeny (female rainbow x male hybrid) were produced and three replicates per family were challenged with IHNV. A significantly higher frequency of two RFLP markers was detected among individuals first to die in one family (C2). MHC polymorphisms have been shown to influence resistance to viral diseases in mammals and chickens. Here we applied single strand conformation polymorphism (SSCP) of the MHC class II beta-chain intron to test for association between MHC allele frequency, IHNV resistance and the two RFLP markers in the same C2 family. None of the associations tested was significant in a preliminary analysis. We plan to increase the power of the analysis by using a larger sample size. SSCP analysis to identify the MHC alleles originating from cutthroat trout is being conducted by comparing samples from the original rainbow and cutthroat trout strains used to produce the hybrid parents.