Characterization of PmHHXM, a New Broad-Spectrum Powdery Mildew Resistance Gene in Chinese Wheat Landrace Honghuaxiaomai

Abstract

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.

Importance of Landraces in Cereal Breeding for Stress Tolerance

“…A multi-pathogen resistance gene, Lr67 , which confers partial resistance to all three wheat rust pathogen species ( Pt , Pst , Pgt ) and powdery mildew ( Bgt ), as demonstrated by using a combination of comparative genomics, mutagenesis and transformation studies, was isolated from a bread wheat landrace (PI250413) [ 124 ]. Wheat landraces have also been studied for other diseases, including Fusarium Head Blight [ 125 ], barley yellow dwarf (BYD) [ 126 ], powdery mildew [ 127 , 128 , 129 ] and stem sawfly [ 130 ]. A recombinant inbred line (RIL) population derived from Haiyanzhong, a Chinese wheat landrace showing a high level of resistance to FHB spread within a spike (type II resistance), has been used to map six QTLs (one major and five minor) and obtain KASP markers useful for MAS [ 125 ].…”