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Title: Major gene for field stem rust resistance co-locates with resistance gene Sr12 in "Thatcher" wheat

item HIEBERT, C - Aafc Lethrdge Research Center
item Kolmer, James
item MCCARTNEY, C - Aafc Lethrdge Research Center
item BRIGGS, JORDAN - University Of Minnesota
item FETCH, T - Aafc Lethrdge Research Center
item BARIANA, H - University Of Sydney
item CHOULET, F - University Of Sydney
item Rouse, Matthew - Matt
item SPIELMEYER, W - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2016
Publication Date: 6/16/2016
Citation: Hiebert, C., Kolmer, J.A., McCartney, C., Briggs, J., Fetch, T., Bariana, H., Choulet, F., Rouse, M.N., Spielmeyer, W. 2016. Major gene for field stem rust resistance co-locates with resistance gene Sr12 in "Thatcher" wheat. PLoS One. 11(6):1-16. doi:10.1371/journal.pone.0157029.

Interpretive Summary: Wheat is attacked by the stem rust fungus, Puccinia graminis tritici. Attacks of stem rust can grealty reduce the yields of wheat in the U.S. and world-wide, threatning food security. The development of stem rust resistant wheat cultivars is the best way to reduce or eliminate losses due to stem rust. A stem rust resistant gene in wheat, Sr12, is present in the wheat cultivar Thatcher that was released in the 1930s in the U.S. Stem rust resistance in Thatcher wheat was determined to be due to the gene Sr12, or another gene that is very closely located to Sr12 on the same chromosome. Sr12 and another gene in wheat called Lr34, work together to give better resistance to stem rust than either gene gives individually. The results of this research can be used to help develop wheat cultivars with better stem rust resistance.

Technical Abstract: Stem rust, caused by Puccinia graminis (Pgt), is a damaging disease of wheat that can be controlled by utilizing effecting stem rust resistance genes. "Thatcher" wheat carries complex resistance to stem rust that is enhanced in the presence of the resistance gene Lr34. The purpose of this study was to examine APR in "Thatcher" and look for genetic interactions with Lr34. A RIL population was tested for stem rust resistance in field nurseries in Canada, USA, and Kenya. BSA was used to find SNP markers associated with reduced stem rust severity. A major QTL was identified on chromosome 3BL near the centromere in all environments. Seedling testing showed that Sr12 mapped to the same region as the QTL for APR. The SNP markers were physically mapped and the region carrying the resistance was searched for sequences with homology to members of the NB-LRR resistance gene family. SNP marker from one NB-LRR-like sequence, NB-LRR3 co-segregated with Sr12. Two additional populations, including one that lacked Lr34 entirely, were tested in field nurseries. NB-LRR3 mapped near the maximum LOD for reduction in stem rust severity in both populations. Lines from a population that segregated for Sr12 and Lr34 were tested for seedling Pgt biomass and infection type, as well as APR to field stem rust which showed an interaction between the genes. We concluded that Sr12, or a gene closely linked to Sr12, was responsible for "Thatcher"-derived APR in several environments and this resistance was enhanced in the presence of Lr34.