<scp> <i>Sr11</i> </scp> ‐Carrying Wheat Variety Yalta Harbours an Additional Locus for Stem Rust Resistance on Chromosome <scp>6B</scp> , Which Is Novel and Distinct From <scp> <i>Sr11</i> </scp>

ABSTRACT Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), remains a significant threat to global wheat production, as new races overcoming deployed resistance genes continue to emerge rapidly. In 2011, the Australian rust surveillance programme detected a new pathotype 34‐1,2,5,7 virulent on stem rust resistance genes Sr5 , Sr6 , Sr7b , Sr9g , Sr11 , Sr15 and Sr17 . Although virulent on Sr11 , this pathotype produced a low infection type (IT 22+c to X) on the Sr11 ‐differential genotype Yalta, suggesting that Yalta carries an uncharacterised resistance ( SrY ) in addition to Sr11 . Genetic analysis and targeted genotype‐by‐sequencing mapping confirmed that Sr11 and SrY are located in the same genomic region (708.66–720.76 Mb) of Chinese Spring IWGSC RefSeq v1.0 and are linked. Based on their linkage and adjacent position, we predicted SrY might be common in wheats carrying Sr11 . We tested 14 lines previously known to carry Sr11 with two specific pathotypes. The tests confirmed the presence of SrY in lines carrying Sr11 . Because avirulence for SrY appears to be rare, it is unlikely to possess any value in breeding for resistance to Pgt. The discovery and characterisation of SrY is, however, useful in distinguishing and separating its effects from other genes conferring resistance to Pgt, avoiding incorrect gene targets in breeding and understanding the evolution of disease resistance and virulence in host plants and rust pathogens.