Molecular Mapping and Chromosomal Location of the Powdery Mildew Resistance Gene in Wheat Cultivar Tangmai 4

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important diseases in wheat (Triticum aestivum L.) worldwide. Breeding for resistance is the most economical and effective method for controlling the disease. Tangmai 4 carries a pair of T1BL·1RS wheat-rye (Secale cereale L.) translocated chromosomes and is resistant to a wide spectrum of wheat powdery mildew isolates. Genetic analysis indicated that a single semidominant gene in Tangmai 4 conferred resistance to powdery mildew, temporarily designated PmTm4. Segregating F2 population and their F3 progenies derived from the cross between Tangmai 4 and Clement were used for bulked segregation analysis. Four SSR, one EST-SSR, and one EST-STS polymorphic markers were linked to the powdery mildew resistance gene PmTm4 in an order of Xcau12–Xgwm611–PmTm4–XEST92–Xbarc1073–Xbarc82. Gene PmTm4 was physically mapped on the distal bin of chromosome 7BL using Chinese Spring nullisomic-tetrasomic, ditelosomic, and deletion lines. The results demonstrate that PmTm4 gene may be either an allele at the Pm5 locus or a member of closely linked cluster of genes.