Molecular mapping of barley genes for resistance to stripe rust

Stripe rust, caused by Puccinia striiformis f. sp. hordei, is one of the most important diseases of barley ( Hordeum vulgare). Growing resistant cultivars is the best approach for controlling stripe rust. Grannenlose Zweizeilige (GZ) and BBA 2890 each have a recessive gene, temporarily designated as rpsGZ in GZ and rps1.a in BBA 2890, conferring seedling resistance against all races of P. striiformis f. sp. hordei identified thus far in the US. Bancroft was one of the first barley cultivars developed in the US with resistance to stripe rust, and has been identified as having durable high-temperature, adult-plant (HTAP) resistance.; To develop molecular maps for the rpsGZ and rps1.a genes, F8 recombinant inbred lines (RILs) were developed from the crosses of Steptoe/GZ and Steptoe/BBA 2890 through single-seed descent. Seedlings of the parents and RILs were evaluated for resistance in the greenhouse. Using 182 F8 RILs, a linkage group for rpsGZ was constructed with 12 resistance gene analog polymorphism (RGAP) markers. Analyses of two sets of wheat-barley chromosome addition lines showed that the gene is on barley chromosome 4H L. Tests with four simple sequence repeat (SSR) markers on chromosome 4H confirmed the gene location and also integrated the RGAP markers into the known SSR linkage map of barley. For the rps1.a gene in BBA 2890, a genetic linkage group was constructed with 13 RGAP and four SSR markers using 150 F8 RILs. The four SSR markers mapped rps1.a on chromosome 3H L. A total of 24 barley cultivars were tested for polymorphisms with the two closest RGAP markers for the resistant allele. These markers detected polymorphism in 88% of the genotypes when used in combination.; To map quantitative trait loci (QTL) for the HTAP resistance, Bancroft was crossed with susceptible Harrington barley. The parents and F4 progeny were evaluated in 2004, and the parents and F5 progeny were evaluated in 2005 in three field sites in Washington State. Infection type (IT) and disease severity (DS) were recorded three times during the growing season. Area under the disease progress curve (AUDPC) was calculated for each parent and progeny based on the DS data. Using 119 F6 lines, a linkage map was constructed for a QTL with eight RGAP markers and three SSR markers, which mapped the QTL on chromosome 3H L. The QTL explained more than 70% of the total variations using DS and AUDPC data. One of the two flanking markers detected polymorphisms in 23 of 26 barley cultivars, indicating that the markers are useful in incorporating the HTAP resistance into most of these cultivars.