Location: Soybean and Nitrogen Fixation ResearchTitle: MlNCD1: A novel Aegilops tauschii derived powdery mildew resistance gene identified in common wheat Author
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2012
Publication Date: 5/1/2012
Citation: Maxwell, J.J., Lyerly, J.H., Srnic, G., Murphy, P., Cowger, C., Parks, W.R., Marshall, D.S., Brown Guedira, G.L., Miranda, L.M. 2012. MlNCD1: A novel Aegilops tauschii derived powdery mildew resistance gene identified in common wheat. Crop Science. 52:1162-1170. Interpretive Summary: Powdery mildew of wheat is a devastating fungal disease that is prevalent in temperate climates. Deployment of resistant cultivars is the preferred method to control this disease but constant changes in the pathogen population require novel sources of resistance and a more efficient utilization of them. In this research, a novel Aegilops tauschii derived powdery mildew resistance gene present in the germplasm line NC96BGTD1 was characterized as a trait controlled by a single gene using two segregating populations from a NC96BGTD1/‘Saluda’ cross (F2 and F4). Molecular markers flanking the disease resistance locus were identified and they were physically mapped to the short arm of chromosome 7D using Chinese Spring aneuploid and deletion stocks. Segregation distortion was observed on most distal markers but this is in agreement with previous reports on the inheritance of alien introgressions in wheat. Based on its chromosomal location, the powdery mildew resistance gene in NC96BGTD1 most likely represents a novel powdery mildew resistance loci but an allelism test with Pm19 will be needed to confirm this. Its effectiveness against powdery mildew populations in the south eastern United States and the newly identified molecular markers make NC96BGTD1 a valuable germplasm source for wheat breeders.
Technical Abstract: Powdery mildew is a major fungal disease in wheat, especially in cool maritime climates. A novel Aegilops tauschii derived wheat powdery mildew resistance gene present in the germplasm line NC96BGTD1 was genetically characterized as a monogenic trait in field trials using F2 and F4-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 cM and 8.3 cM distal to the resistance gene in the F2 and F4 generations, respectively. Xgpw328 mapped 16.2 cM proximal to the resistance gene in the F2 and 13.6 cM proximal to the resistance gene in the F4 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 F4 generation with markers distal to the resistance gene showing a preference for the Ae. 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.