Identification and characterization of , a tetraploid wheat gene that confers resistance to the Ug99 stem rust race group.

The f. sp. () Ug99 race group is virulent to most stem rust resistance genes currently deployed in wheat and poses a threat to global wheat production. The durum wheat ( ssp. ) gene confers resistance to Ug99 and other virulent races, and is more effective at high temperatures. Using map-based cloning, we delimited a candidate region including two linked genes encoding coiled-coil nucleotide-binding leucine-rich repeat proteins designated CNL3 and CNL13. Three independent truncation mutations identified in each of these genes demonstrated that only was required for Ug99 resistance. Transformation of an 8-kb genomic sequence including into the susceptible wheat variety Fielder was sufficient to confer resistance to Ug99, confirming that is transcripts were slightly down-regulated 2-6 days after inoculation and were not affected by temperature. By contrast, six pathogenesis-related () genes were up-regulated at high temperatures only when both and were present, suggesting that they may contribute to the high temperature resistance mechanism. We identified three -resistant haplotypes, which were present in one-third of cultivated emmer and durum wheats but absent in most tested common wheats (). These results suggest that can be used to improve Ug99 resistance in a large proportion of modern wheat cultivars. To accelerate its deployment, we developed a diagnostic marker for The identification of expands the number of -resistance genes that can be incorporated into multigene transgenic cassettes to control this devastating disease.