Vegetative compatibility groups within Fusarium oxysporum f.sp. lini from Linum usitatissimum (flax) wilt nurseries in western Canada

Following the discovery of substantial differences in the development and severity of Fusarium wilt in Linum usitatissimum L. (flax) wilt nurseries in western Canada, a study of the population structure of Fusarium oxysporum f.sp. lini (Bolley) Snyd. & Hans using vegetative compatibility analysis was initiated. Vegetative compatibility was determined using nitrate non-utilizing mutants. From a total of 105 isolates, 74 were assigned to 12 vegetative compatibility groups (VCG 0440-04411), 22 were not compatible with any other isolates and 9 did not produce mutants. The populations of F. oxysporum f.sp. lini in Fusarium wilt nurseries in western Canada were significantly different. There was a predominant VCG in each of the nurseries, which was either nonexistent or not common in other nurseries, VCG 0440 in Indian Head, 0441 in Treherne, 0442 in Morden-80, 0443 in Saskatoon, and 0444 in Morden-60. There were only three overlapping VCGs; VCG 0440 was common to Morden-60 and Indian Head and VCGs 0442 and 0444 were common to Morden-60 and Morden-80. The differences in disease development and severity observed previously may be due to the differences in the population structure of the pathogen. These findings have significant implications for the approaches to breeding for Fusarium wilt resistance in flax.