Twenty four isolates of Fusarium graminearum, half of which were 3-acetyldeoxynivalenol (3-ADON) and half 15-acetyldeoxynivalenol (15-ADON) chemotypes, were tested for their ability to produce deoxynivalenol and to cause Fusarium head blight (FHB) in spring wheat cultivars. The objectives of this study were to determine (1) whether 3-ADON isolates differ in aggressiveness, as measured by the FHB index, and DON production from 15-ADON isolates under field conditions, and (2) whether the performance of resistant host cultivars was stable across isolates. Field tests of all isolates were conducted with three replicates at each of two locations in Canada and Germany in 2008 with three host genotypes differing in FHB resistance level. The resistant host genotype showed resistance regardless of the chemotype or location. The differences between mean FHB indices of 3-ADON and 15-ADON isolates were not significant for any wheat genotype. In contrast, average DON production by the 3-ADON isolates (10.44 mg kg −1 ) was significantly (P<0.05) higher than for the 15-ADON isolates (6.95 mg kg −1 ) at three of the four locations where moderately resistant lines were tested, and at both locations where susceptible lines were evaluated. These results indicate that 3-ADON isolates could pose a greater risk to food safety. However, as the mean aggressiveness and DON production of 3-ADON and 15-ADON chemotypes was similar on highly resistant lines, breeding and use of highly resistant lines is still the most effective measure of reducing the risks associated with DON in wheat.
Two BC3F2:5 winter wheat populations carrying Fusarium head blight (FHB) resistance quantitative trait loci (QTL) Fhb1 and Qfhs.ifa‐5A were tested for resistance and agronomic and baking‐quality performance in 10 high yielding environments. The objectives of this study were to determine (i) the resistance effect of the two nonadapted QTL, (ii) their side effects on agronomic and quality performance, and (iii) their relative advantage in European breeding programs. The two populations were split into four QTL classes containing either Fhb1, Qfhs.ifa‐5A, both QTL or neither of them with about 25 (Opus BC3F2:5 population) and 15 (Anthus BC3F2:5 population) lines each class and check varieties. Disease resistance trials on microplots and yield trials on large plots had two replicates at five locations in Germany in each of 2 yr. Mean FHB ratings (%) between QTL classes carrying either one or two QTL showed significantly (p < 0.05) improved FHB resistance and a significant variation within QTL classes. Small significant negative effects on grain yield were detected in the Anthus but not in the Opus BC3F2:5 population. However, selection of lines with improved resistance level and similar high yield level like the recurrent parent was feasible. All other differences in agronomic and quality traits were in all cases small although often significant. The introgression of both QTL did not significantly improve the FHB resistance compared to Qfhs.ifa‐5A indicating that this QTL suffices for European breeding programs.
Competitive Aggressiveness in Binary Mixtures of Fusarium graminearum and F. culmorum Isolates Inoculated on Spring Wheat with Highly Effective Resistance QTL Christiane hristiane Von der on der Ohe he and Thomas homas Miedaner iedaner AbstractFusarium head blight (FHB) caused by Fusarium graminearum and F. culmorum is a devastating disease with high effects on grain yield and quality. We developed spring wheat lines incorporating the highly effective FHB resistance quantitative trait loci (QTL) Fhb1 and Qfhs.ifa-5A. Whether these QTL lead to competition within Fusarium populations in the field resulting in isolates with higher aggressiveness has not been analysed. The aims of this study were to determine (i) the aggressiveness potential of F. graminearum and F. culmorum isolates, (ii) competition effects of these isolates in binary mixtures and (iii) the stability of resistant hosts. Six F. graminearum, two F. culmorum isolates and seven binary mixtures containing these isolates were tested for their aggressiveness and mycotoxin production at two locations in South Germany in 2007 and 2008. Host lines were four spring wheat lines containing the resistance QTL Fhb1 and ⁄ or Qfhs.ifa-5A or none of them and one standard variety. Re-isolates were sampled from plots inoculated with the binary mixtures to identify the percentage of each isolate in the mixture by simple sequence repeat markers. Resistant host lines reacted as expected and had a high stability to all isolates and mixtures. Only less important host · mixture interactions were detected. Aggressiveness among isolates and mixtures was significantly different. Type and amount of mycotoxin and high single isolate aggressiveness were not necessarily advantageous in the mixture. However, both F. culmorum isolates outcompeted F. graminearum isolates. Significant deviations from the inoculated 1 : 1 proportions occurred in 34 of 49 cases, illustrating that competition effects appeared in the mixtures. These differences depended mainly on the year and not on the level of host resistance. We conclude that resistance should not be affected by the Fusarium isolates and mixtures.
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