Powdery mildew, caused by the biotrophic fungal pathogen Blumeria graminis f. sp. tritici (Bgt), is a globally important wheat disease causing severe yield losses, and deployment of resistant varieties is the preferred choice for managing this disease. Chinese wheat landrace Datoumai was resistant to 22 of 23 Bgt isolates at the seedling stage. Genetic analysis based on the inoculation of Bgt isolate E09 on the F1, F2, and F2:3 populations derived from the cross Datoumai × Huixianhong revealed that the powdery mildew resistance of Datoumai is controlled by a single dominant gene, temporarily designated as PmDTM. Bulked segregant analysis and simple sequence repeat mapping with 200 F2 plants showed that PmDTM was located in the same genetic region as Pm24 on chromosome 1DS. To fine map PmDTM, 12 critical recombinants were identified from 1,192 F2 plants and delimited PmDTM to a 0.5-cM Xhnu58800 to Xhnu59000 interval covering 180.5 Kb (38,728,125 to 38,908,656 bp) on chromosome 1DS, and only one highly confident gene, TraesCS1D02G058900, was annotated within this region. TraesCS1D02G058900 encodes a receptor-like serine/threonine-protein kinase (STK), and a 6-bp deletion in exon 5 may confer the resistance to powdery mildew. Allele frequency analysis indicated that the STK allele with 6-bp deletion was only present in three landraces (Datoumai, Chiyacao [Pm24], and Hulutou) and was absent in all of the 353 Chinese modern cultivars and 147 foreign cultivars. These results demonstrate that PmDTM is mapped to the same locus as Pm24 and can be widely used to enhance powdery mildew resistance in wheat growing regions worldwide.

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Powdery mildew, caused by fungal pathogen Blumeria graminis f. sp. tritici (Bgt), is one of agronomically important and widespread wheat diseases causing severe yield losses. Deployment of broad‐spectrum disease-resistance genes is the preferred strategy to prevent this pathogen. Chinese wheat landrace Honghuaxiaomai (HHXM) was resistant to all 23 tested Bgt isolates at the seedling stage. The F1, F2, and F2:3 progenies derived from the cross HHXM × Yangmai 158 were used in this study, and genetic analysis revealed that a single dominant gene, designated as PmHHXM, conferred resistance to Bgt isolate E09. Bulked segregant analysis and molecular mapping initially located PmHHXM to the distal region of chromosome 4AL. To fine map PmHHXM, two critical recombinants were identified from 592 F2 plants and delimited PmHHXM to a 0.18-cM Xkasp475200–Xhnu552 interval covering 1.77-Mb, in which a number of disease resistance-related gene clusters were annotated. Comparative mapping of this interval revealed a perturbed synteny among Triticeae species. This study reports the new powdery mildew resistance gene PmHHXM that seems different from three known QTL/genes identified on chromosome 4AL and has significant values for further genetic improvement. Analysis of the polymorphisms of 13 co-segregating markers between HHXM and 170 modern wheat cultivars indicates that Xhnu227 and Xsts478700 developed here are ideal for marker-assisted introgression of this resistance gene in wheat breeding.

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