Variation For Fusarium Head Blight Resistance Research Articles

Molecular Characterization and Expression of PFT, an FHB Resistance Gene at the Fhb1 QTL in Wheat.

Fusarium head blight (FHB) is a destructive fungal disease in wheat worldwide. Efforts have been carried out to combat this disease, and the pore-forming toxin-like (PFT) gene at the quantitative trait locus (QTL) Fhb1 was isolated and found to confer resistance to FHB in Sumai 3. In this study, we characterized PFT in 348 wheat accessions. Four haplotypes of PFT were identified. The wild haplotype of PFT had higher resistance than other haplotypes and explained 13.8% of phenotypic variation in FHB resistance by association analysis. PFT was highly expressed during early flowering and increased after Fusarium graminearum treatment in Sumai 3. Analysis of the 5' flanking sequence of PFT predicted that the cis elements of the PFT promoter were related to hormones and biological defense responses. However, PFT existed not only in the FHB-resistant accessions but also in some susceptible accessions. These results suggested that FHB resistance in a diverse range of wheat genotypes is partially conditioned by PFT. The profiling of FHB resistance and the PFT locus in this large collection of wheat germplasm may prove helpful for incorporating FHB resistance into wheat breeding programs, although more work is needed to reveal the exact role of the QTL Fhb1 in conferring resistance to fungal spread.

Variations for Fusarium head blight resistance associated with genomic diversity in different sources of the resistant wheat cultivar 'Sumai 3'.

Fusarium head blight (FHB), caused by Fusarium graminearum, is a serious disease of wheat (Triticum aestivum L.) associated with contamination by the mycotoxin deoxynivalenol (DON). The FHB-resistant wheat cultivar ‘Sumai 3’ has been used extensively around the world. The existence of variation in FHB resistance among ‘Sumai 3’ accessions has been discussed. In this study, genetic variation among ‘Sumai 3’ accessions collected from six countries were identified using SSR markers; our results demonstrate unique chromosome regions in Sumai 3-AUT and Sumai 3-JPN (‘Sumai 3’ accessions from Austria and Japan, respectively). Field evaluation indicated strong resistance to FHB in Sumai 3-AUT. The polymorphic rate (number of polymorphic markers/number of available markers × 100) based on a DArT array was 12.5% between the two ‘Sumai 3’ accessions. Genotyping for DNA markers flanking FHB-resistant quantitative trait loci (QTLs) revealed genetic variations for the QTL regions on 5AS and 2DS; however, no variation was observed for the QTL regions on 3BS and 6B. Thus, the variation in FHB resistance among ‘Sumai 3’ accessions in the field is due to genetic diversity.

Quantitative Trait Locus Mapping of Increased Fusarium Head Blight Susceptibility Associated with a Wild Emmer Wheat Chromosome

Chromosome 2A of wild emmer wheat (Triticum turgidum var. dicoccoides) genotype Israel A increases Fusarium head blight (FHB) severity when present in durum wheat (T. turgidum var. durum) cv. Langdon (LDN). The goal of this study was to identify regions of Israel A chromosome 2A associated with this difference in resistance. A recombinant inbred chromosome line population (RICL) from a cross between LDN and the LDN-Israel A chromosome 2A substitution line [LDN(DIC-2A)] was employed for analysis. Three greenhouse FHB evaluations were completed on the RICL to obtain phenotypic data on variation for FHB resistance, and a simple sequence repeat (SSR)-based molecular map of chromosome 2A was developed. Quantitative trait locus (QTL) mapping identified a region on the long arm of chromosome 2A that was associated with FHB resistance in each independent FHB evaluation. Depending on the evaluation, the single best SSR marker in this region accounted for between 21 and 26% of the variation for FHB resistance, with the Israel A marker alleles associated with increased FHB susceptibility. The single best markers from each evaluation reside within an interval of approximately 22 cM. This study identifies one or more new QTL on chromosome 2A in tetraploid wheat that can contribute to significant variation in FHB resistance.

Marker-based introduction of three quantitative-trait loci conferring resistance to Fusarium head blight into an independent elite winter wheat breeding population

Fusarium head blight (FHB) is one of the most important wheat diseases that causes yield and quality losses as well as contamination with deoxynivalenol (DON). This study aimed for marker-based introduction of three previously mapped QTLs from two German winter wheat resistance sources into an elite background unrelated to the mapping population. A double cross (DC) served as initial population that combined two resistance donor-QTL alleles from "Dream" (Qfhs.lfl-6AL, Qfhs.lfl-7BS) and one donor-QTL allele from "G16-92" on chromosome 2BL with two high yielding, susceptible elite winter wheats ("Brando", "LP235.1"). The initial population of 600 DC-derived F(1) lines was selected with SSR markers for the respective QTLs. After two marker-selection steps, each of eight marker classes was represented by 9-22 lines possessing the respective donor-QTL allele or all possible combinations thereof in the homozygous state. The effect of the QTLs was estimated by field tests at four locations inoculated with Fusarium culmorum. Resistance was measured as the mean of multiple FHB ratings (0-100%). Marker classes incorporating only one QTL were not significantly more resistant than the class without any QTL, the combination of two donor-QTL alleles reduced FHB significantly. On average, lines with Qfhs.lfl-6AL were significantly taller than lines without this QTL. A considerable variation for FHB resistance was found in all marker classes. Marker-based introduction of two QTLs enhanced mean FHB rating by about 40 percentage points, the selected plants, however, were, on average, significantly taller. Both findings strongly support a phenotypic selection following after marker-based introduction of effective QTLs.

Components of resistance to fusarium head blight (FHB) in wheat detected in a seed‐germination assay with Microdochium majus and the relationship to FHB disease development and mycotoxin accumulation from Fusarium graminearum infection

Components of partial disease resistance (PDR) to fusarium head blight (FHB), detected in a seed‐germination assay, were compared with whole‐plant FHB resistance of 30 USA soft red winter wheat entries in the 2002 Uniform Southern FHB Nursery. Highly significant (P < 0·001) differences between cultivars in the in vitro seed‐germination assay inoculated with Microdochium majus were correlated to FHB disease incidence (r = −0·41; P < 0·05), severity (r = −0·47; P < 0·01), FHB index (r = −0·46; P < 0·01), damaged kernels (r = −0·52; P < 0·01), grain deoxynivalenol (DON) concentration (r = −0·40; P < 0·05) and incidence/severity/kernel‐damage index (ISK) (r = −0·45; P < 0·01) caused by Fusarium graminearum. Multiple linear regression analysis explained a greater percentage of variation in FHB resistance using the seed‐germination assay and the previously reported detached‐leaf assay PDR components as explanatory factors. Shorter incubation periods, longer latent periods, shorter lesion lengths in the detached‐leaf assay and higher germination rates in the seed‐germination assay were related to greater FHB resistance across all disease variables, collectively explaining 62% of variation for incidence, 49% for severity, 56% for F. graminearum‐damaged kernels (FDK), 39% for DON and 59% for ISK index. Incubation period was most strongly related to disease incidence and the early stages of infection, while resistance detected in the seed germination assay and latent period were more strongly related to FHB disease severity. Resistance detected using the seed‐germination assay was notable as it related to greater decline in the level of FDK and a smaller reduction in DON than would have been expected from the reduction in FHB disease assessed by visual symptoms.

Influence of inoculation method and growth stage on fusarium head blight in barley

The effect of inoculation method and growth stage on the development of fusarium head blight (FHB) in barley were evaluated under controlled conditions. Barley cvs. Argyle, AC Oxbow, Chevron, and AC Lacombe were inoculated with macroconidial suspensions of Fusarium graminearum Schwabe either by single floret injection at preanthesis, anthesis, or postanthesis or by spray application to the entire spike at heading, 7 days after heading, or 14 days after heading. Four weeks after inoculation, heads were evaluated visually for symptoms of FHB, then the spikes were hand threshed and the seed assayed for F. graminearum colonization. Visual determination of FHB generally overestimated the F. graminearum seed colonization in the injected spikes and underestimated it in sprayed spikes. Infection resulting from floret injection was limited to the inoculated spikelet and immediately adjacent spikelets, so variation in FHB resistance among cultivars could not be satisfactorily distinguished using this inoculation method. The growth stage at the time of floret injection had no effect on seed colonization by F. graminearum. Spray inoculations produced more seed colonized by F. graminearum than single floret injection and was better for distinguishing the levels of resistance in the cultivars. The most resistant cultivar, AC Oxbow, could be distinguished from the other cultivars, using this inoculation method. Although the plants were susceptible to FHB infection from heading to 14 days after heading, the cultivars were best differentiated by inoculating at 14 days after heading. Seed colonization by F. graminearum among the first, second, or third tillers was similar using either inoculation method.