Mapping of Fusarium head blight resistance in two winter wheat populations and gene expression analysis of putative genes related to the host-pathogen interaction
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Fusarium graminearum (Fg) is the primary causal agent of Fusarium head blight (FHB) in wheat. Resistance to FHB is complex and involves multiple genes with relatively small effects. A winter wheat line, 32c*17, demonstrated strong FHB and deoxynivalenol (DON) resistance. Two quantitative trait loci (QTL) mapping studies were conducted using two doubled haploid populations (32c*17/Peregrine (3CPR) and 18I*45/32c*17 (8I3C)) tested for FHB resistance in field and greenhouse trials. In the 3CPR population, three main QTL for FHB resistance on chromosomes 4D, 6A and 6D were detected. Markers for QTL on chromosomes 4D, 6B and 6D accurately predicted FHB resistance in the reciprocal cross. In the 8I3C population, two major 4B and 6D QTL for disease incidence (Inc) and DON content and one major 7A QTL for disease severity (Sev) were identified. The 32c*17 allele on chromosome 4B in the 8I3C population increased height, reduced anther retention, Inc and DON content, while no 4B QTL was detected in the 3CPR population. The 32c*17-derived 6D QTL was identified in both 8I3C and 3CPR populations. Moreover, the 8I3C 4D QTL for height and the 3CPR 4D QTL for FHB resistance were detected in the similar region. Height QTL on chromosomes 1D, 2B and 7B in the 8I3C population were not associated with FHB resistance. A gene expression study was conducted to wheat-Fg interaction on five genotypes which included two near isogenic lines carrying either the Rht-B1a or Rht-B1b allele and three checks Sumai 3, 32c*17 and Caledonia. For four Trichothecene (TRI) genes (TRI5, TRI6, TRI12 and TRI101) examined, lower gene expression in genotypes with high disease severity were found in the inoculated spikelets in the point-inoculated Fg treatment. Higher expression of the three genes (ABCC6, AOS and PR4) at earlier time points (3 dai) and a lower expression level of NFXL1 at the late time point may be associated with FHB resistance in all three inoculation treatments, while late expression of the same three genes might be insufficient to reduce disease severity.