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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Cereal Crops Research » Research » Publications at this Location » Publication #233451
Title: Identification and validation of SSR markers linked to the stem rust resistance gene Sr6 on the short arm of chromosome 2D in wheat

Author
item TSILO, TOI - UNIV. OF MINNESOTA
item Chao, Shiaoman
item Jin, Yue
item ANDERSON, JAMES - UNIV. OF MINNESOTA

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2008
Publication Date: 2/1/2009
Citation: Tsilo, T., Chao, S., Jin, Y., Anderson, J. 2009. Identification and validation of SSR markers linked to the stem rust resistance gene Sr6 on the short arm of chromosome 2D in wheat. Theoretical and Applied Genetics. 118:515-524

Interpretive Summary: Stem rust historically has been the most significant disease of wheat worldwide. The most effective approach to control this type of disease is to develop varieties carrying more than one resistance gene, thus, providing prolonged resistance against several different races. The wheat stem rust resistance gene Sr6, present in several wheat cultivars, confers a high level of resistance against a wide range of stem rust races. The expression of Sr6 resistance is influenced by temperature, light intensity, and genetic background of the recipient genotype. Here, we report the identification and validation of diagnostic moleculear markers linked to Sr6 that can be used for the detection of this gene in wheat breeding programs. A mapping population was developed and screened for stem rust reaction in the seedling stage. These materials were then used to screen 418 microsatellite markers that covered the entire genome of wheat. Two markers closely linked to Sr6 were identified, and were diagnostic for Sr6 in a diverse set of 46 wheat accessions and breeding lines developed in Australia, Canada, China, Egypt, Ethiopia, Kenya, Mexico, South Africa, and USA. These diagnostic markers will be useful for marker-assisted selection of Sr6. In particular, the recent studies have indicated that lines carrying Sr6 alone are susceptible to race TTKS (or Ug99), which is the most devastating race of stem rust that currently poses threat to wheat production worldwide. Therefore, Sr6-specific markers identified in this study will be useful in pyramiding Sr6 with other Sr genes, especially those that are resistant to races TTKS and its derivatives.

Technical Abstract: The wheat stem rust resistance gene Sr6, present in several wheat cultivars, confers a high level of resistance against a wide range of races of Puccinia graminis f. sp. tritici. The inheritance and expression of the Sr6 gene is complex. Resistance conferred by Sr6 is influenced by temperature, light intensity, and genetic background of the recipient genotype. Here, we report the identification and validation of diagnostic molecular markers linked to Sr6 that can be used for the detection of this gene in wheat breeding programs. A mapping population of 136 F2 plants and their F2:3 families derived from a cross between near-isogenic lines, ‘Chinese Spring’ and ISr6-Ra, were screened for stem rust reaction in the seedling stage. A bulked segregant analysis (BSA) based on seedling tests was used to screen 418 SSR markers that covered the entire genome of wheat. Four markers, Xwmc453, Xcfd43, Xcfd77, and Xgwm484, were mapped within a chromosome region that spanned 9.7cM from Sr6. The closest markers, Xwmc453 and Xcfd43, were linked to Sr6 at a distance of 1.1cM and 1.5 cM, respectively. The markers Xwmc453 and Xcfd43 amplified Sr6-specific maker alleles that were diagnostic for Sr6 in a diverse set of 50 wheat accessions and breeding lines developed in Australia, Canada, China, Egypt, Ethiopia, Kenya, Mexico, South Africa, and USA. These diagnostic markers can now be used for marker-assisted selection of Sr6 and for pyramiding it with other stem rust resistance genes.