IDENTIFICATION OF QUANTITATIVE TRAIT LOCI ASSOCIATED WITH IHN VIRUS RESISTANCE IN RAINBOW TROUT (Oncorhynchus mykiss)

¹ Department of Aquatic Biosciences, Tokyo University of Fisheries, 4-5-7 Konan, Minato, Tokyo 108-8477, Japan

² Mikawaichinomiya Station, Freshwater Resources Research Center, Aichi Fisheries Research Institute, Hoi, Aichi 441-1222, Japan

³ Fuji Trout Hatchery, Shizuoka Prefectural Fisheries Experimental Station, Fujinomiya, Shizuoka 418-0108, Japan

Infectious haematopoietic necrosis (IHN) is an acute, systemic, and virulent rhabdoviral disease that occurs in the salmonid species. The attempt to produce a specific strain of salmonid that is IHN virus (IHNV) resistant has not been successful due to the limited knowledge and complexity of the polygenic trait. The recent development of rainbow trout genetic linkage maps has made it possible to dissect genetically complex traits. In this study, we mapped quantitative trait loci (QTL) for IHNV resistance in a segregated population of backcross derived from out-crossing the resistant Oizumi strain with the susceptible Hourai strain of rainbow trout. QTL analysis was based on a microsatellite linkage map containing 93 loci with 25 linkage groups. P values were calculated using the Pearson goodness of fit Chi-square to identify the chromosomal regions associated with IHNV resistance. A significant QTL represented by a cluster of four microsatellite markers was mapped on linkage group 2 (P = 0.011). This result expands our knowledge of the inheritance of complex quantitative traits involved in the viral disease of the salmonids and provides the first information towards marker-assisted selection (MAS) for breeding IHN resistant rainbow trout.