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United States Department of Agriculture

Agricultural Research Service

Research Project: CEREAL RUST FUNGI: GENETICS, POPULATION BIOLOGY, AND HOST-PATHOGEN INTERACTIONS

Location: Cereal Disease Laboratory

Title: Inheritance of resistance to Ug99 stem rust in wheat cultivar Norin 40 and genetic mapping of Sr42

Authors
item Ghazvini, Habibollah -
item Hiebert, Colin -
item Zegeye, Taye -
item Liu, Sixin -
item Dilawari, Mridull -
item Anderson, James -
item Rouse, Matthew
item Jin, Yue
item Fetch, Thomas -

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 19, 2012
Publication Date: May 12, 2012
Citation: Ghazvini, H., Hiebert, C.W., Zegeye, T., Liu, S., Dilawari, M., Anderson, J.A., Rouse, M.N., Jin, Y., Fetch, T. 2012. Inheritance of resistance to Ug99 stem rust in wheat cultivar Norin 40 and genetic mapping of Sr42. Journal of Theoretical and Applied Genetics. 125:817–824.

Interpretive Summary: Stem rust, caused by Puccinia graminis f. sp. tritici, is a devastating disease of wheat. The emergence of race TTKSK (Ug99)and new variants in Africa threatens wheat production worldwide. The best method of controlling stem rust is to deploy effective resistance genes in wheat cultivars. Few stem rust resistance (Sr) genes derived from the primary gene pool of wheat confer resistance to TTKSK. Norin 40, which carries Sr42, is resistant to TTKSK and variant TTKST. The goal of this study was to elucidate the inheritance of resistance to Ug99 in Norin 40 and map the gene(s). A doubled haploid (DH) population of LMPG-6/Norin 40 was evaluated for resistance to race TTKST. Segregation of 248 DH lines fit a 1:1 ratio ('21:1= 0.58, p = 0.45), indicating a single gene in Norin 40 conditioned resistance to Ug99. This was confirmed by an independent F2:3 population also derived from the cross LMPG-6/Norin 40 where a 1:2:1 ratio ('21:2:1= 0.69, p = 0.71) was observed following inoculation with race TTKSK. Mapping with DNA markers located this gene to chromosome 6DS, the known location of Sr42. PCR marker FSD_RSA co-segregated with Sr42, and simple sequence repeat (SSR) marker BARC183 was closely linked (0.5 cM) to Sr42. A previous study found close linkage between FSD_RSA and SrCad, a temporarily designated gene that also confers resistance to Ug99, thus Sr42 may be the same gene or allelic. Two markers identified in this study (FSD_RSA and BARC183) are suitable for marker assisted selection (MAS) in wheat breeding programs to improve stem rust resistance to Ug99.

Technical Abstract: Stem rust, caused by the fungus Puccinia graminis f. sp. tritici, is a devastating disease of wheat. The emergence of a race of Puccinia graminis f. sp. tritici known as Ug99, and new Ug99 variants in Africa threaten wheat production worldwide. The best method of controlling stem rust is to use genetic resistance. Few stem rust resistance (Sr) genes are available for use in agriculture. Wheat line Norin 40, which carries Sr42, is resistant to Ug99 and variants. The goal of this study was to elucidate the inheritance of resistance to Ug99 in Norin 40 and determine the chromosome location of the gene(s). Two types of wheat populations derived from Norin 40 and susceptible line LMPG-6 were tested for reaction to Ug99. Segregation of resistance in both of these populations indicated a single gene conferred resistance in Norin 40 to Ug99: Sr42. Cosegregation of resistance and DNA markers located on chromosome arm 6DS identified the location of Sr42. A previous study found close linkage between the same DNA markers and SrCad, a temporarily designated gene that also confers resistance to Ug99, thus Sr42 may be the same gene. Two markers identified in this study (FSD_RSA and BARC183) are suitable for marker assisted selection (MAS) in wheat breeding programs to improve stem rust resistance to Ug99.

Last Modified: 12/18/2014