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.
Highlights
Wheat accounts for approximately 30% of the global cereal consumption (FAO: World Agriculture: towards 2015/2030), and is of fundamental importance for food security
We report the identification of a powdery mildew resistance gene MlIW172 derived from wild emmer and mapping the gene to chromosome arm 7AL
The IW172 wild emmer accession was highly resistant to the E09 Blumeria graminis f. sp. tritici (Bgt) isolate (IT value 0), whereas durum wheat line Mo75 was highly susceptible (IT value 4)
Summary
Wheat accounts for approximately 30% of the global cereal consumption (FAO: World Agriculture: towards 2015/2030), 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. Development of resistant cultivars containing single or stacked resistance genes is a major focus of wheat breeding program because growth of such cultivars has proved to be the most effective agronomic approach to control disease losses. More than 60 powdery mildew resistance genes/alleles have been identified at 43 loci (Pm1 – Pm50, Pm18 = Pm1c, Pm22 = Pm1e, Pm23 = Pm4c, Pm31 = Pm21) in wheat and its wild relatives [2,3,4]
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