Mapping and characterization of two stem rust resistance genes derived from cultivated emmer wheat accession PI 193883

Authors: SHARMA, JYOTI - Agriculture And Agri-Food Canada; ZHANG, QIJUN - North Dakota State University; Rouse, Matthew; Klindworth, Daryl; Friesen, Timothy; LONG, YUNMING - North Dakota State University; OLIVERA, PABLO - University Of Minnesota; Jin, Yue; MCCLEAN, PHILLIP - North Dakota State University; Xu, Steven; Faris, Justin

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2019
Publication Date: 9/7/2019
Citation: Sharma, J.S., Zhang, Q., Rouse, M.N., Klindworth, D.L., Friesen, T.L., Long, Y., Olivera, P.D., Jin, Y., McClean, P.E., Xu, S.S., Faris, J.D. 2019. Mapping and characterization of two stem rust resistance genes derived from cultivated emmer wheat accession PI 193883. Theoretical and Applied Genetics. https://doi.org/10.1007/s00122-019-03417-x.
DOI: https://doi.org/10.1007/s00122-019-03417-x

Interpretive Summary: The fungal disease known as stem rust is a serious threat to worldwide wheat production and global food security. A group of fungal strains known as Ug99 are particularly concerning because there are few wheat genes known to condition resistance to them. Here, researchers conducted genetic studies on an early form of domesticated wheat known as cultivated emmer that is resistant to Ug99 strains, and they found that it harbors two stem rust resistance genes that had not been identified previously. The researchers determined the locations of the two genes within the cultivated emmer genome, and they developed molecular markers associated with the genes that can be used as tools to monitor the introgression of the genes into modern wheat varieties through conventional crossing techniques. The results of this research will allow wheat breeders to develop new bread wheat and durum wheat varieties that are resistant to the devastating effects of stem rust, and thus provide security to the global food supply.

Technical Abstract: The wheat research community consistently strives to identify new genes that confer resistance to stem rust caused by the fungal pathogen Puccinia graminis f. sp. tritici Eriks & E. Henn (Pgt). In the current study, our objective was to identify and genetically characterize the stem rust resistance derived from the cultivated emmer accession PI 193883. A recombinant inbred line (RIL) population developed from a cross between the susceptible durum wheat line Rusty and PI 193883 was genotyped and evaluated for reaction to Pgt races TTKSK, TRTTF, and TMLKC. Two QTL conferring resistance were identified on chromosome arms 2BL (QSr.fcu-2B) and 6AL (QSr.fcu-6A). The stem rust resistance gene (Sr883-2B) underlying QSr.fcu-2B was recessive and novel based on its physical location. QSr.fcu-6A was located in the Sr13 region, but PI 193883 is known to carry the susceptible haplotype S4 for Sr13, indicating that the gene underlying QSr.fcu-6A (Sr883-6A) is likely a new gene residing close to Sr13. Three IWGSC scaffold-based simple sequence repeat (SSR) and two SNP-based semi-thermal asymmetric reverse PCR (STARP) markers were developed for the Sr883-2B region, and one STARP marker was developed for Sr883-6A. Sr883-2B was epistatic to Sr883-6A for reaction to TTKSK and TRTTF, and the two genes had additive effects for TMLKC. These two genes and the markers developed in this research provide additional resources and tools for the improvement of stem rust resistance in durum and common wheat breeding programs.