Septoria linicola (Speg) Garassini (teliolmorph Mycosphaerella linorum Naumov) causes the disease pasmo in flax in many flax growing areas. The effects of fungicide application and inoculation on flax under field conditions were studied on six varieties at Morden, Manitoba at the Agriculture and Agri-Food Canada Research Station as well as at Winnipeg, Manitoba at the University of Manitoba Field Station during the 2003 and 2004 growing seasons. Yield, seed oil and protein content and 1000 kernel weight were generally reduced under heavy infections for most cultivars.;The use of fungicides increased yield significantly for almost all the cultivars in all years when compared to a control with no fungicide application. Area under the disease progress curve (AUDPC) was also significantly reduced for all fungicide application treatments except for the inoculated with fungicide application treatment in 2004. Seed oil content was significantly improved for all fungicide application treatments in all years for all cultivars except Norlin in 2003. Seed protein content did not show any clear response to fungicide application. Thousand kernel weight was significantly positively affected by the application of fungicides for all treatments in all years except for the cultivar Vimy at the Winnipeg site in 2003.;The structure of two S. linicola populations in Manitoba was studied using Random Amplified Polymorphic DNA (RAPD), a PCR based molecular marker system. Plants were collected from two commercial fields in Portage and Sanford and used to generate single spore isolates for use in this study. The level of polymorphism detected using RAPD suggests that it is plausible that there is sexual recombination occurring between the two populations, or that there is extensive movement of individual isolates throughout the province. Limited grouping based on site was seen in the dendrograms. Analysis of Molecular Variance (AMOVA) revealed that 88% of the total genetic variation was due to within population variation and 12% to between population variation. This suggests a mix of clonal and sexual reproduction during the growing season.
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