MlNCD1 : A Novel Aegilops tauschii ‐Derived Powdery Mildew Resistance Gene Identified in Common Wheat

Powdery mildew is a major fungal disease in wheat, especially in cool maritime climates. A novel Aegilops tauschii Coss.‐derived wheat powdery mildew resistance gene present in the germplasm line NC96BGTD1 was genetically characterized as a monogenic trait in field trials using F 2 – and F 4 –derived lines from a NC96BGTD1 × ‘Saluda’ cross. Simple sequence repeat (SSR) markers were used to map and tag the resistance gene present in NC96BGTD1. Two dominant SSR markers flanking the resistance gene were identified. Xgwm635 mapped 5.5 and 8.3 cM distal to the resistance gene in the F 2 and F 4 generations, respectively. Xgpw328 mapped 16.2 cM proximal to the resistance gene in the F 2 and 13.6 cM proximal to the resistance gene in the F 4 generation. These SSR markers were previously mapped to the short arm of chromosome 7D and their positions were confirmed using Chinese Spring aneuploid and deletion stocks. Significant segregation distortion was observed in the F 4 generation with markers distal to the resistance gene showing a preference for the A. tauschii alleles while markers proximal to the resistance gene showed less significant preference for Saluda alleles. Only the adult plant resistance gene Pm38 has been mapped to the short arm of chromosome 7D but to a more proximal position than the gene in NC96BGTD1. The resistance gene described herein should be temporarily designated MlNCD1 .