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United States Department of Agriculture

Agricultural Research Service

Title: Microsatellite markers linked to stem rust resistance allele Sr9a in wheat

Authors
item Tsilo, Toi - UNIVERSITY OF MINNESOTA
item Jin, Yue
item Anderson, James - UNIVERSITY OF MINNESOTA

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2007
Publication Date: September 1, 2007
Repository URL: http://hdl.handle.net/10113/8823
Citation: Tsilo, T.J., Jin, Y., Anderson, J.A. 2007. Microsatellite markers linked to stem rust resistance allele Sr9a in wheat. Crop Science. 47:2013-2020.

Interpretive Summary: Stem rust of wheat is one of the most serious diseases of wheat worldwide. Host resistance is more effective and durable when several stem rust resistance (Sr) genes are pyramided into a single genotype, a process that can be facilitated by marker-assisted selection. Here we studied the Sr9a allele, one of the six (identified with suffixes a-g) alleles at the Sr9 locus on chromosome 2BL, using 116 F2's derived from the cross of near-isogenic lines, "Chinese Spring" and ISr9a-Ra. Three co-dominant microsatellite markers, Xgwm47, Xgwm120 and Xbarc101, that mapped within 3.6 cM proximal to the Sr9a allele were identified, with Xgwm47 being the closest marker to Sr9a. A dominant microsatellite marker, Xwmc175, co-segregated in repulsion phase with the Sr9a allele. Fifty-nine wheat accessions were screened with the 3 co-dominant markers to determine their polymorphism information content (PIC). The marker locus Xgwm47 revealed 12 alleles had the highest PIC value of 0.85. Attempts were made to postulate the presence of Sr9a using phenotypic screening. However, in accessions that had multiple Sr genes, it was not possible to postulate Sr9a due to masking effects. Despite the ambiguity of phenotypic evaluation, Xgwm47 was diagnostic for Sr9a in additional NILs tested. These results suggest that Xgwm47 will be a useful tool for the marker-assisted selection of Sr9a in wheat breeding programs, and will facilitate the further investigation of the complex Sr9a locus.

Technical Abstract: Stem rust of wheat, caused by Puccinia graminis Pers.: Pers. f.sp. tritici Eriks. & E Henn., is one of the most serious diseases of wheat worldwide. Host resistance is more effective and durable when several stem rust resistance (Sr) genes are pyramided into a single genotype, a process that can be facilitated by marker-assisted selection. Here we studied the Sr9a allele, one of the six (identified with suffixes a-g) alleles at the Sr9 locus on chromosome 2BL, using 116 F2's derived from the cross of near-isogenic lines, "Chinese Spring" and ISr9a-Ra. Three co-dominant microsatellite markers, Xgwm47, Xgwm120 and Xbarc101, that mapped within 3.6 cM proximal to the Sr9a allele were identified, with Xgwm47 being the closest marker to Sr9a. A dominant microsatellite marker, Xwmc175, co-segregated in repulsion phase with the Sr9a allele. Fifty-nine wheat accessions were screened with the 3 co-dominant markers to determine their polymorphism information content (PIC). The marker locus Xgwm47 revealed 12 alleles and had the highest PIC value of 0.85. Attempts were made to postulate the presence of Sr9a using phenotypic screening. However, in accessions that had multiple Sr genes, it was not possible to postulate Sr9a due to masking effects. Despite the ambiguity of phenotypic evaluation, Xgwm47 was diagnostic for Sr9a in additional NILs tested. These results suggest that Xgwm47 will be a useful tool for the marker-assisted selection of Sr9a in wheat breeding programs, and will facilitate the further investigation of the complex Sr9a locus.

Last Modified: 4/18/2014
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