Origin and Dynamics of , a Wheat Gene for Resistance to Nonadapted Pathotypes of .

Avirulence of isolates of on common wheat is conditioned by at least five avirulence genes. One is corresponding to resistance gene located on chromosome 1D. We identified a resistance gene corresponding to a second avirulence gene, , and named it (). was closely linked to . A survey of the population of , the D genome donor to common wheat, revealed that some accessions from the southern coastal region of the Caspian Sea, the birthplace of common wheat, carried both genes. and carriers accounted for 65 and 80%, respectively, of accessions in a common wheat landrace collection. The most likely explanation of our results is that both resistance genes were simultaneously introduced into common wheat at the time of hybridization of and . . However, a prominent difference was recognized in their geographical distributions in modern wheat; and co-occurred at high frequencies in regions to the east of the Caspian Sea, whereas occurred at a lower frequency than in regions to the west. This difference was considered to be associated with range of pathotypes to which these genes were effective. . accessions carrying and also carried , another resistance gene involved in the species specificity. We suggest that the gain of the D genome should have given an adaptive advantage to the genus by conferring disease resistance.