Cultivars resistant to flax wilt caused by Fusarium oxysporum f. sp. lini (Bolley) Snyd. & Hans. have reduced the disease severity in North America (Kommedahl et al. 1970). Annual disease surveys in western Canada showed that disease incidence ranges from traces to 20%, and severity ranges from traces to 10% (Rashid et al 2002 & 2000). Flax wilt continues to be a problem since the pathogen is genetically diverse (Mpofu & Rashid 2005, Borlaug 1945). Prevalent use of resistant cultivars exerts selection pressure on the pathogen population and causes pathogenic and ecological adaptations.