Development of a diagnostic co-dominant marker for stem rust resistance gene Sr47 introgressed from Aegilops speltoides into durum wheat

Authors: YU, GUOTAI - North Dakota State University; Klindworth, Daryl; Friesen, Timothy; Faris, Justin; ZHONG, SHAOBIN - North Dakota State University; RASMUSSEN, JACK - North Dakota State University; Xu, Steven

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2015
Publication Date: 8/11/2015
Publication URL: https://handle.nal.usda.gov/10113/62628
Citation: Yu, G., Klindworth, D.L., Friesen, T.L., Faris, J.D., Zhong, S., Rasmussen, J.B., Xu, S.S. 2015. Development of a diagnostic co-dominant marker for stem rust resistance gene Sr47 introgressed from Aegilops speltoides into durum wheat. Theoretical and Applied Genetics. 128:2367-2374.

Interpretive Summary: Wheat stem rust resistance gene Sr47, originally transferred from goatgrass species Aegilops speltoides into durum wheat, is highly resistant to many strains of stem rust pathogen. Using a limited number of molecular markers, we previously located the gene to the long arm of chromosome 2B in durum wheat. However, the molecular markers that are currently available are not efficient for use in breeding. The objective of this study was to develop new molecular markers that could be efficiently used by wheat breeders to select Sr47 in durum and bread wheat breeding programs. In this research, we first analyzed the wheat DNA sequences in the chromosomal region harboring Sr47 and its related region in model species (rice and false brome grass) in various database systems that store DNA sequences. Based on the matched DNA sequences between wheat and the model species, we developed a DNA marker (designated as Xrwgs38) that is tightly linked to Sr47. The stem rust evaluation and marker analysis on a population of the durum wheat plants segregating for Sr47 demonstrated that this new marker can clearly differentiate the plants carrying Sr47 from other plants. A validation test showed that Xrwgs38 was diagnostic for Sr47 in all 62 durum and common wheat cultivars/lines tested. This study demonstrated that Xrwgs38 will greatly facilitate the selection of Sr47 in durum and common wheat breeding.

Technical Abstract: Stem rust (caused by Puccinia graminis f. sp. tritici, abbreviated as Pgt) resistance gene Sr47, originally transferred from Aegilops speltoides to durum wheat (Triticum turgidum subsp. durum) line DAS15, confers a high level of resistance to Pgt race TTKSK (known as Ug99). Recently, the durum Rusty 5D(5B) substitution line was used to reduce the Ae. speltoides segment, and the resulting lines had Sr47 on small Ae. speltoides segments on wheat chromosome arm 2BL. The objective of this study was to develop a robust marker for marker-assisted selection of Sr47. A 200 kb segment of the Brachypodium distachyon genome syntenic with the Sr47 region was used to identify wheat expressed sequence tags (ESTs) homologous to the B. distachyon genes. The wheat EST sequences were then used to develop sequence-tagged site (STS) markers. By analyzing the markers for polymorphism between Rusty and DAS15, we identified a co-dominant STS marker, designated as Xrwgs38, which amplified 175-bp and 187-bp fragments from wheat chromosome 2B and Ae. speltoides chromosome 2S segments, respectively. The marker cosegregated with the Ae. speltoides segments carrying Sr47 in the four families derived from four BC2F1 plants with the pedigree of Rusty/3/Rusty 5D(5B)/DAS15//47-1 5D(5B). Analysis of 62 durum and common wheat cultivars/lines lacking the Sr47 segment indicated that they all possessed the 175-bp allele of Xrwgs38, indicating that it is diagnostic for the small Ae. speltoides segment carrying Sr47. This study demonstrated that Xrwgs38 will greatly facilitate the selection of Sr47 in durum and common wheat breeding.