PLASMA-PROTEIN LEVELS AS POTENTIAL MARKER TRAITS FOR RESISTANCE TO FURUNCULOSIS

The feasibility of including individual records on correlated traits in a family selection programme which aims to increase resistance to furunculosis in Atlantic salmon was studied; markers were selected because of their potential role in the pathogenesis of the disease. Fibrinogen and alpha(2)-antiplasmin both show genetic variation; both are correlated with survival after challenge with Aeromonas salmonicida, the correlation being 0.44 and 0.37 (P < 0.05), respectively, and it is possible to measure both on a large scale at low costs. Contrary to alpha(2)-antiplasmin, fibrinogen was negatively correlated with survival due to furunculosis within the 10 most resistant Families and within the 10 most susceptible families in contrast to an overall positive correlation. This inconsistency could be attributable to the presence of different allelic phases in different families, and of major linked Loci influencing survival and fibrinogen levels. Thus, only alpha(2)-antiplasmin fulfils the requirements for a marker trait for resistance to the disease suitable for individual selection at the population level, whereas the use of fibrinogen would be restricted to within family selection. The full statistical model explained 51% of the variation in resistance to furunculosis, and alpha(2)-antiplasmin contributed 15% to this variation when considered as a separate entity. Thus, the additional gain from including individual records on alpha(2)-antiplasmin in a family selection programme could be significant.