Genetics and mapping of stem rust resistance to Ug99 in the wheat cultivar Webster

Abstract

New races of wheat stem rust, namely TTKSK (Ug99) and its variants, pose a threat to wheat production in the regions where they are found. The accession of the wheat cultivar Webster (RL6201) maintained at the Cereal Research Centre in Winnipeg, Canada, shows resistance to TTKSK and other races of stem rust. The purpose of this study was to study the inheritance of seedling resistance to stem rust in RL6201 and genetically map the resistance genes using microsatellite (SSR) markers. A population was produced by crossing the stem rust susceptible line RL6071 with Webster. The F(2) and F(3) were tested with TPMK, a stem rust race native to North America. The F(3) was also tested with TTKSK. Two independently assorting genes were identified in RL6201. Resistance to TPMK was conferred by Sr30, which was mapped with microsatellites on chromosome 5DL. The second gene, temporarily designated SrWeb, conferred resistance to TTKSK. SrWeb was mapped to chromosome 2BL using SSR markers. Comparison with previous genetic maps showed that SrWeb occupies a locus near Sr9. Further analysis will be required to determine if SrWeb is a new gene or an allele of a previously identified gene.

Discovery and molecular mapping of a new gene conferring resistance to stem rust, Sr53, derived from Aegilops geniculata and characterization of spontaneous translocation stocks with reduced alien chromatin

“…We were able to further define the position of Sr53 to approximately FL 0.33 of 5M g L by the development of interstitial recombinants, aided by new molecular markers, the development and characterization of additional populations, and genomic in situ hybridization. The only other wheat stem rust resistance gene reported on the long arm of chromosome 5D is Sr30, which was previously mapped distal to SSR markers CFD12 and GWM182 on 5DL (Kaur et al 2009;Hiebert et al 2010a), and represents a different locus. Among the three resistant recombinants, U6200-117 has the shortest 5M g L alien chromatin with a FL of 0.33; U6200-64 has a 5M g L FL of 0.46; and U6154-124 has an interstitial translocation with FL 0.16-0.47.…”

“…Gene pyramiding is facilitated by the ability to use molecular markers closely or completely linked to resistance genes. Molecular markers have been developed for numerous stem rust resistance genes, including: Sr2 (Spielmeyer et al 2003;Hayden et al 2004;Mago et al 2011), Sr6 (Tsilo et al 2009), Sr9a (Tsilo et al 2007), Sr13 (Admassu et al 2011;Simons et al 2011), Sr22 (Khan et al 2005;Olson et al 2010;Periyannan et al 2011), Sr24 (Mago et al 2005), Sr25 (Liu et al 2010), Sr26 (Mago et al 2005;Liu et al 2010), Sr30 (Hiebert et al 2010a), Sr31 (Das et al 2006;Weng et al 2007), Sr32 (Bariana et al 2001), Sr33 (Sambasivam et al 2008), Sr35 (Zhang et al 2010), Sr36 (Bariana et al 2001;Tsilo et al 2008), Sr39 (Gold et al 1999;Mago et al 2009;Niu et al 2011), Sr40 (Wu et al 2009), Sr45 (Sambasivam et al 2008), Sr50 (synonym SrR, Anugrahwati et al 2008), Sr51 (Liu et al 2011), Sr52 (Qi et al 2011), SrCad (Hiebert et al 2010b), and SrWeb (Hiebert et al 2010a). Recent progress on molecular marker development and improved donor sources should accelerate the pyramiding and deployment of cultivars with more durable resistance to stem rust.…”

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“…However, 2BL also harbour Sr9, Sr28 and Sr16. Hiebert et al, (2010) mapped gene Srweb on 2BL with Xgwm47 as the closest marker at 1.4 cM. Sr9 was also mapped on 2BL and Xgwm47 was the closest marker at the distance of 0.9 cM (Tsilo et al, 2007).…”

“…Bariana et al, (2001) also mapped Sr30 to 5DL in cultivar Cranbrook, Hiebert et al, (2010) mapped Sr30 in Webster to 5DL. The closest marker Xcfd12 linked to Sr30 was found monomorphic in the NI5439/WR95 population.…”

Genetics and molecular mapping of stem rust resistance in bread wheat line WR95

“…2). The marker Xgwm47 is linked to both Sr9 and Srweb at distance of 0.9 cM (Tsilo et al 2007) and 1.4 cM (Hiebert et al 2010) respectively. Therefore, the F 2 population was also genotyped with Xgwm47 to determine distance between dominant gene in WR95 and Sr9/Srweb.…”