Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2006
Publication Date: 6/12/2006
Citation: Yan, G., Chen, X. 2006. Molecular mapping of a recessive barley gene for resistance to stripe rust. Theor. Appl. Genet. 113:529-537. Interpretive Summary: Barley stripe rust is one of the most important barley diseases in the south central and western USA. The disease is best controlled using resistant cultivars. Barley germplasm Grannenlose Zweizeilige (GZ) has a recessive gene (rpsGZ) effective against all races of the barley stripe rust pathogen identified so far in the USA. To identify molecular markers for mapping the resistance gene, a mapping population of 182 recombinant inbred lines (RILs) was developed from a cross between GZ and Steptoe, an adapted cultivar but susceptible to stripe rust. The parental and RIL seedlings of the cross were evaluated for resistance to two races of the pathogen under controlled greenhouse conditions. Genomic DNA was extracted from the parents and the RILs. The resistance gene analog polymorphism (RGAP) technique developed in our lab was used to identify molecular markers for the resistance gene. A linkage group for the gene was constructed with 12 RGAP markers, of which four markers either completely co-segregated with the resistance locus or were tightly linked to the resistance gene. Analyses of barley chromosome addition lines of wheat with two RGAP markers identified the location of the gene on the long arm of barley chromosome 4H. The results also were confirmed with four microsatellite markers that are specific to the long arm of that chromosome. The molecular markers and information on chromosomal location should be useful in develop barley cultivars with stripe rust resistance.
Technical Abstract: Barley stripe rust, caused by Puccinia striiformis f. sp. hordei, is one of the most important barley (Hordeum vulgare) diseases in the south central and western United States of America. The disease is best controlled using resistant cultivars. Barley genotype Grannenlose Zweizeilige (GZ) has a recessive gene (rpsGZ) that is effective against all races of P. striiformis f. sp. hordei identified so far in the USA. To develop a molecular map for mapping the gene, F8 recombinant inbred lines (RILs) were developed from the Steptoe X GZ cross through single-seed descent. Seedlings of the parents and RILs were evaluated for resistance to races PSH-14 and PSH-54 of P. striiformis f. sp. hordei under controlled greenhouse conditions. Genomic DNA was extracted from the parents and 182 F8 RILs and used for cosegregation analysis. The resistance gene analog polymorphism (RGAP) technique was used to identify molecular markers for rpsGZ. A linkage group for the gene was constructed with 12 RGAP markers, of which two markers were completely co-segregating with the resistance locus, and two markers were closely linked to the locus with a genetic distance of 0.9 and 2.0 cM, respectively. These four markers were present only in the susceptible parent. The closest marker to the resistance allele was 11.7 cM away. Analyses of two sets of barley chromosome addition lines of wheat with the two RGAP markers that were cosegregating with the susceptibility allele showed that rpsGZ and the markers were located on the long arm of barley chromosome 4H. Further, tests with four simple sequence repeat (SSR) markers confirmed the chromosomal location of the rpsGZ gene and also integrated the RGAP markers into the known SSR-based linkage map of barley. The closest SSR marker EBmac0679 had a genetic distance of 7.5 cM with the gene in the integrated linkage map constructed with the 12 RGAP markers and 4 SSR markers.