Resistance reaction of flax germplasm to fusarium wilt.
The fusarium wilt pathogen, Fusarium oxysporum f. sp. lini (Fol), is able to survive in soil for long periods and cause considerable yield loss. Varietal resistance is the most effective method to control the disease and it is essential to identify resistant cultivars and genes. Disease reaction of a subset (160) of RIL lines developed from parent cultivars ‘Aurore’ (moderately resistant) and ‘Oliver’ (susceptible) was assessed under controlled environment conditions to two Fol isolates (isolate numbers 81 and 131). Disease severity (DS) was determined (grading scale, 0 to 9) and the area under the disease progress curve (AUDPC) was calculated. The population varied from resistant to highly susceptible; 5 to 14% of the RILs severely wilted (scores of 8 and 9) with isolates 131 and 81, respectively. Similarly, in wilt nurseries, at Saskatoon and Morden, evaluation of the full set of 200 RILs, the disease reaction varied from resistant to susceptible, with 21% and 33% of RILs severely wilted, respectively, at the green boll stage. These results indicate genetic variation among the RILs for DS and AUDPC. The results from the two locations were significantly different, although moderately correlated (r2=0.6127). Differences in environmental and experimental conditions (such as seeding date) at the two locations, as well as different Fol strains in the soil combined with the subjectivity of the grading system may explain the significant differences between locations.
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