ARS | Publication request: Stem rust resistance in A-genome diploid relatives of wheat

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2011
Publication Date: August 1, 2011
Citation: Rouse, M., Jin, Y. 2011. Stem rust resistance in A-genome diploid relatives of wheat. Plant Disease. 95:941-944.

Interpretive Summary: Wheat stem rust is an important disease and the control of stem rust in wheat relies on the use of genetic resistance. A new race designated TTKSK (also known as Ug99) renders many resistance genes ineffective. The objective of this study was to identify stem rust resistance genes in wild relatives of wheat so that the genes could be transferred to wheat in breeding for stem rust resistance. We screened 1061 accessions of T. monococcum and 214 accessions of T. urartu against race TTKSK and four additional races and found a large proportion of the accessions (78.7% of T. monococcum and 93.0% of T. urartu) were resistant to TTKSK. Among these resistant accessions, 55 T. monococcum accessions (6.4% of the total) were also resistant to the other four races. Associations of resistance to different races in T. monococcum indicated the presence of genes conferring resistance to multiple races. Comparing the infection type patterns observed to the expected patterns of known genes indicated that previously uncharacterized resistance genes to race TTKSK exist in both T. monococcum and T. urartu. These new sources of resistance will provide useful genes for improving wheat for stem rust resistance.

Technical Abstract: Wheat stem rust caused by Puccinia graminis f. sp. tritici, has been effectively controlled through the use of genetic resistance. The recently identified race TTKSK (Ug99) possesses virulence to many resistance genes that have been used in wheat breeding worldwide. One strategy to aid breeders in developing resistant varieties is to utilize resistance genes transferred from wild relatives to wheat. Stem rust resistance genes have previously been introgressed from Triticum monococcum to wheat. In order to identify additional resistance genes, we screened 1061 accessions of T. monococcum and 214 accessions of T. urartu against race TTKSK and four additional races: TTTTF, TRTTF, QFCSC, and MCCFC of P. graminis f. sp. tritici. A large proportion of the accessions (78.7% of T. monococcum and 93.0% of T. urartu) were resistant to TTKSK with infection types ranging from 0 to 2+. Among these resistant accessions, 55 T. monococcum accessions (6.4% of the total) were also resistant to the other four races. Associations of resistance to different races in T. monococcum indicated the presence of genes conferring resistance to multiple races. Comparing the infection type patterns observed to the expected patterns of known genes indicated that previously uncharacterized resistance genes to race TTKSK exist in both T. monococcum and T. urartu.