2008 Annual Report 1a.Objectives (from AD-416) The objectives of this cooperative research project are to:. 1)Complete the development of rainbow trout breeding stocks that consist of true-breeding individuals for the cecropin gene, a gene which increases disease resistance;. 2)Complete the identification and characterization of genes in rainbow trout macrophage cells that are responsive to induction by cecropin B, and;. 3)Develop rainbow trout broodstock for aquaculture with enhanced muscle growth by down-regulating the MSTN-1 gene. 1b.Approach (from AD-416) Bacterial and viral pathogens will be used to challenge F2 transgenic fish and those that exhibit resistance to one or more of the pathogens will be bred together as the initial stages for development of a true-breeding stock. In addition, the production of gynogens from the eggs of resistant animals will be attempted to shorten the time to make the genes completely homozygous. Rainbow trout macrophages will be treated with cecropins and the expression of genes will be monitored by the use of cDNA subtraction hybridization. This technique will allow the identification of the genes which play a role in the adaptive immune response in rainbow trout. Finally, the development of rainbow trout broodstock with increased muscle growth will be attempted by use of the RNAi gene constructs to down-regulate the MSTN gene. Preliminary results suggest that this approach will lead to strains with enhanced somatic growth rate, reducing the costs for care, feeding and rearing space. 3.Progress Report Several lines of fish with targeted transgenes for disease resistance have reached their third generation and were shown to have enhanced resistance to both bacterial (Aeromonas salmonicida) and viral (IHNV) pathogens. Studies also indicated the gene cecropin B could serve as an adjuvant to improve DNA vaccination. Monitoring was accomplished via telephone discussions and periodic written reports. National Program 106, Component 3, Genetic Improvement.