Abstract
BackgroundFusarium head blight (FHB) is a devastating disease of wheat worldwide. Resistance to FHB is quantitatively controlled by the combined effects of many small to medium effect QTL. Flowering traits, especially the extent of extruded anthers, are strongly associated with FHB resistance.ResultsTo characterize the genetic basis of FHB resistance, we generated and analyzed phenotypic and gene expression data on the response to Fusarium graminearum (Fg) infection in 96 European winter wheat genotypes, including several lines containing introgressions from the highly resistant Asian cultivar Sumai3. The 96 lines represented a broad range in FHB resistance and were assigned to sub-groups based on their phenotypic FHB severity score. Comparative analyses were conducted to connect sub-group-specific expression profiles in response to Fg infection with FHB resistance level. Collectively, over 12,300 wheat genes were Fusarium responsive. The core set of genes induced in response to Fg was common across different resistance groups, indicating that the activation of basal defense response mechanisms was largely independent of the resistance level of the wheat line. Fg-induced genes tended to have higher expression levels in more susceptible genotypes. Compared to the more susceptible non-Sumai3 lines, the Sumai3-derivatives demonstrated higher constitutive expression of genes associated with cell wall and plant-type secondary cell wall biogenesis and higher constitutive and Fg-induced expression of genes involved in terpene metabolism. Gene expression analysis of the FHB QTL Qfhs.ifa-5A identified a constitutively expressed gene encoding a stress response NST1-like protein (TraesCS5A01G211300LC) as a candidate gene for FHB resistance. NST1 genes are key regulators of secondary cell wall biosynthesis in anther endothecium cells. Whether the stress response NST1-like gene affects anther extrusion, thereby affecting FHB resistance, needs further investigation.ConclusionInduced and preexisting cell wall components and terpene metabolites contribute to resistance and limit fungal colonization early on. In contrast, excessive gene expression directs plant defense response towards programmed cell death which favors necrotrophic growth of the Fg pathogen and could thus lead to increased fungal colonization.
Highlights
Fusarium head blight (FHB) is a devastating disease of wheat worldwide
1300 (10.6%) FRGs were shared by the R, Moderate Resistant (MR) and SUS group, but not by the Sumai3 resistance group (Fig. 2D)
This result corroborates with Pan et al [28], Biselli et al [26], and Wang et al [17], in which the majority of the Fusarium graminearum (Fg)-induced genes were shared by all wheat genotypes, with higher expression levels typically found in more susceptible lines
Summary
Fusarium head blight (FHB) is a devastating disease of wheat worldwide. Resistance to FHB is quantitatively controlled by the combined effects of many small to medium effect QTL. Fusarium head blight (FHB), predominately caused by Fusarium graminearum, is one of the most destructive diseases of wheat and small grain cereals worldwide. FHB resistance is a quantitative trait, with more than 500 QTL reported in previous studies [3,4,5]. The Chinese spring wheat cultivar Sumai is among the most important and best characterized sources of FHB resistance and is the donor of the two major resistance QTL Fhb and Qfhs.ifa-5A [6]. The second resistance locus, Qfhs.ifa-5A was recently fine-mapped into the major effect QTL Qhfs.ifa-5Ac located on the centromere and the minor effect QTL Qfhs.ifa-5AS on the short arm of chromosome 5A [10]
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