2010 Annual Report
Objective 1: Establish two domesticated strains (even year and odd year populations) of rainbow trout selectively bred for improved growth and disease resistance and estimate genetic and phenotypic parameters for commercially important traits.
A selective breeding program for improved growth performance in one line of trout and resistance to Flavobacterium psychrophilum in a second was established resulting in significant improvements in growth performance and disease resistance in the respective lines. This also provided initial characterization for a variety of traits including growth performance traits, survival in response to a F. psychrophilum and Yersinia ruckeri challenge, and stress responses. We established that resistance to F. psychrophilum and growth can be made simultaneously and determined differences in growth performance was similar among our laboratory conditions and a variety of grow-out conditions. Our growth selected line will continue in our upcoming project and the disease resistant line has been turned over to project 1930-32000-002-00D for further selection and characterization.
Objective 2: Provide physiological definition and characterization of growth, stress, and reproductive traits in rainbow trout.
Thermal growth coefficient (TGC) calculated over the month prior to the fish reaching the most common market size of 450 g at 10 months correlated better with future growth than did relative size at 10 months. Therefore enabling selection for growth at larger sizes without maintaining fish to a larger size. TGC was observed to be heritable, therefore it was incorporated into selection for the growth line.
Plasma levels of the growth hormone axis hormones, GH and IGF-I were shown to correlate with measures of growth performance suggesting measures of the hormones might serve as a basis for selection to improve growth or feed efficiency.
Characterization of stress responses of our selected lines revealed plasma cortisol levels were positively correlated with growth performance and stressing fish before a disease challenge could affect ranking of families for resistance. Observation of phenotypes in successive generation provided evidence of major genes affecting stress response. Based on this progress, project 1930-31000-009-00D will search for QTL for variation in post-stressor plasma cortisol levels in the next project cycle.
Objective 3: Develop techniques for effective polyploidy induction to disrupt sexual development in rainbow trout.
Procedures for inducing tetraploidy were significantly improved in rainbow trout. Success can be greatly increased if the time to apply pressure based on the first cleavage interval (FCI) is determined for each clutch of eggs. Project 1930-31000-010-00D will investigate the basis for variation in FCI among fish and evaluate performance of triploid fish derived from tetraploids.