Aquaculture production of salmonids, particularly intensively cultured rainbow trout, is severely impacted by infectious hematopoietic necrosis (IHN), a rhabdoviral disease. Despite considerable efforts to manage the disease, no approved or accepted control measures are available for the commercial industry. We propose to examine the inter- and intra- specific genetic variation present in rainbow and cutthroat trout, and their reciprocal hybrids, for resistance to IHN virus. Within rainbow trout we will produce 10 half-sib sire groups each consisting of 3 full-sib families. Replicated exposures to a standard IHN virus isolate and subsequent monitoring of mortality will enable us to quantify the additive genetic variation present within our stocks for this trait. We will also examine the specific resistance of cutthroat trout from Henry's Lake, Idaho, a stock we believe to exhibit high levels of resistance to IHN infection, and hybrids between this species and rainbow trout through direct immersion challenges of progeny from controlled matings. Additionally, we will explore DNA fingerprint band variability between species and among individuals segregating for IHN resistance in an effort to develop a DNA marker linked to IHN resistance.
Anticipated Results:Success in either aspect of this project will lead to the development of IHN resistant rainbow trout strains through genetic improvement, either by traditional selective breeding procedures or by interspecific gene introgression from cutthroat trout. Identification of a DNA marker linked to IHN resistance would significantly reduce the time required to develop resistant strains. Reduction of IHN mortalities and associated losses will potentially save the U.S. rainbow trout industry millions of dollars annually.
