Location: Crop Improvement and Genetics ResearchTitle: Fine physical and genetic mapping of powdery mildew resistance gene MlIW172 originating from wild emmer(Triticum dicoccoides) ) Author
Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/22/2014
Publication Date: 6/23/2014
Citation: Ouyang, S., Zhang, D., Han, J., Zhao, X., Cui, Y., Song, W., Huo, N., Liang, Y., Xie, J., Wang, Z., Wu, Q., Chen, Y., Lu, P., Zhang, D., Wang, L., Sun, H., Yang, T., Keeble-Gagnere, G., Appels, R., Dolezel, J., Ling, H., Luo, M., Gu, Y.Q., Sun, X., Liu, Z. 2014. Fine physical and genetic mapping of powdery mildew resistance gene MlIW172 originating from wild emmer (Triticum dicoccoides). PLoS One. 9:e100160. Interpretive Summary: Wheat accounts for approximately 30% of the global cereal consumption, and is of fundamental importance for food security. Ensuring the yield increase of wheat to meet future needs has become an important focus in agricultural research. Powdery mildew, caused by a fungus pathogen, Blumeria graminis f. sp. triticii , is one of the most devastating diseases of common wheat worldwide. In this study, a single dominant powdery mildew resistance gene MlIW172 was identified in a wild emmer wheat species, and mapped to the distal region of chromosome arm 7AL. Sequencing of a targeted region containing this resistance locus identified gene sequences similar to those resistance-like genes previously identified in rice and Brachypodium. Further cloning and characterization of the resistance gene will provide a novel approach to improve wheat's disease resistance phenotype against this devastating pathogen.
Technical Abstract: Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important wheat diseases in the world. In this study, a single dominant powdery mildew resistance gene MlIW172 was identified in the IW172 wild emmer accession and mapped to the distal region of chromosome arm 7AL (bin7AL-16-0.86-0.90) via molecular marker analysis. MlIW172 was closely linked with the RFLP probe Xpsr680-derived STS marker Xmag2185 and the EST markers BE405531 and BE637476. This suggested that MlIW172 might be allelic to the Pm1 locus or a new locus closely linked to Pm1. By screening genomic BAC library of durum wheat cv. Langdon and 7AL-specific BAC library of hexaploid wheat cv. Chinese Spring, and after analyzing genome scaffolds of Triticum urartu containing the marker sequences, additional markers were developed to construct a fine genetic linkage map on the MlIW172 locus region and to delineate the resistance gene within a 0.48 cM interval. Comparative genetics analyses using ESTs and RFLP probe sequences flanking the MlIW172 region against other grass species revealed a general co-linearity in this region with the orthologous genomic regions of rice chromosome 6, Brachypodium chromosome 1, and sorghum chromosome 10. However, orthologous resistance gene-like RGA sequences were only present in wheat and Brachypodium. The BAC contigs and sequence scaffolds that we have developed provide a framework for the physical mapping and map-based cloning of MlIW172.