Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Database with DON resistance data for DH populations and wheat varieties and breeding lines

We investigated the hypothesis that resistance to deoxynivalenol (DON) is a major resistance factor in the Fusarium head blight (FHB) resistance complex of wheat. Ninety-six double haploid (DH) lines from a cross between “CM82036” and “Remus” were examined. “CM82036” originates from a cross “Sumai-3/Thornbird-6”. The DH lines were tested for DON resistance after application of the toxin in the ear, and for resistances to initial infection and spread of FHB after artificial inoculation with Fusarium. Toxin application to flowering ears induced typical FHB symptoms. QTL analyses detected one locus with a major effect on DON resistance (LOD = 53.1, R2 = 92.6). The DON resistance phenotype was closely associated with an important FHB resistance QTL, Qfhs.ndsu-3BS, which was previously identified as governing resistance to spread of symptoms in the ear. Resistance to the toxin was correlated with resistance to spread of FHB (r = 0.74, P<0.001). In resistant wheat lines the applied toxin was converted to DON-3-O-glucoside as the detoxification product.

There was a close relation between the [DON-3-glucoside]/[DON] ratio and DON resistance in the toxin treated ears (R2 = 0.84). We conclude that resistance to DON is important in the FHB resistance complex and hypothesize that Qfhs.ndsu-3BS either encodes a DON-glucosyl-transferase or regulates the expression of such an enzyme. Investigations of a second wheat population, including most known wheat genotypes with a high resistance level to FHB, showed that the wheat lines “Sumai3”, “Nobeokabozu”, “Wuhan” and their derivatives expressed high resistance to DON. Also in these lines the applied toxin was converted to DON-3-O-glucoside. These data showed the latter mechanism of DON detoxification is a common mechanism present in all DON resistance wheat lines identified so far.

Results are published. The DON resistant lines described are commonly available for research and resistance breeding.

Total FHB resistance in wheat can be dissected into several resistance components. Resistances to initial infection (resistance component type I) and spread of FHB in the host (type II) are commonly accepted. Resistance component type III was described as insensitivity of wheat lines to the toxin, defined as the ability of the resistant cultivar to degrade DON. So far it was not clear whether DON resistance in wheat exists and whether it substantially contributes to FHB resistance in general. In this contribution we could not only show that DON resistance significantly increases FHB resistance, but we could also elucidate the biochemical mechanism of DON resistance.

For practical breeding these findings might have several consequences. We know that the DON-producing ability of the Fusarium isolates correlates well with their virulence. It is expected that the introduction of DON resistance to wheat will reduce pathogen virulence and will increase total FHB resistance, leading to less symptoms and lower DON contamination levels relative to DON susceptible wheat cultivars. The DON conjugate formed in DON resistant lines was indeed found in both artificially inoculated and naturally infected wheat samples. Yet, results obtained with a small set of wheat lines revealed that although resistant cultivars contained higher amounts of DON-glucoside, total content of DON + DON-glucoside is an order of magnitude larger in DON- and Fusarium-susceptible wheat cultivars. The biochemical fate of DON-3-O-glucoside in human and animal intestinal tracts is currently unclear. DON-3-O-glucoside produced in DON-resistant wheat lines could be a so called “masked mycotoxin”, which is not detectable with routine analyses but which might regain its biological activity after the glucose moiety is cleaved off in the intestinal tract. In this respect it is interesting to mention that the cultivar Sumai-3 , which contains the major QTL for FHB resistance Qfhs.ndsu-3BS, is the most widely used resistance source in the world.

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