Simultaneous transfer, introgression, and genomic localization of genes for resistance to stem rust race TTKSK (Ug99) from Aegilops tauschii to wheat

Abstract

Wheat production is currently threatened by widely virulent races of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, that are part of the TTKSK (also known as 'Ug99') race group. The diploid D genome donor species Aegilops tauschii (2n = 2x = 14, DD) is a readily accessible source of resistance to TTKSK and its derivatives that can be transferred to hexaploid wheat, Triticum aestivum (2n = 6x = 42, AABBDD). To expedite transfer of TTKSK resistance from Ae. tauschii, a direct hybridization approach was undertaken that integrates gene transfer, mapping, and introgression into one process. Direct crossing of Ae. tauschii accessions with an elite wheat breeding line combines the steps of gene transfer and introgression while development of mapping populations during gene transfer enables the identification of closely linked markers. Direct crosses were made using TTKSK-resistant Ae. tauschii accessions TA1662 and PI 603225 as males and a stem rust-susceptible T. aestivum breeding line, KS05HW14, as a female. Embryo rescue enabled recovery of F1 (ABDD) plants that were backcrossed as females to the hexaploid recurrent parent. Stem rust-resistant BC1F1 plants from each Ae. tauschii donor source were used as males to generate BC2F1 mapping populations. Bulked segregant analysis of BC2F1 genotypes was performed using 70 SSR loci distributed across the D genome. Using this approach, stem rust resistance genes from both accessions were located on chromosome arm 1DS and mapped using SSR and EST-STS markers. An allelism test indicated the stem rust resistance gene transferred from PI 603225 is Sr33. Race specificity suggests the stem rust resistance gene transferred from TA1662 is unique and this gene has been temporarily designated SrTA1662. Stem rust resistance genes derived from TA1662 and PI 603225 have been made available with selectable molecular markers in genetic backgrounds suitable for stem rust resistance breeding.

Genotype-by-sequencing facilitates genetic mapping of a stem rust resistance locus in Aegilops umbellulata, a wild relative of cultivated wheat

“…searsii Feldman & Kislev ex K. Hammer , and Ae. geniculata into wheat; these are Sr51 [26], Sr53 [27], SrTA1662 [28], SrTA10171 [29] and SrTA10187 [29]. …”

Polyploidization enhancing genetic recombination of the ancestral diploid genome in the evolution of hexaploid wheat

“…Ae. tauschii is a widely distributed (van Slageren, 1994) and genetically diverse species (Lubbers et al, 1991; Dvorak et al, 1998; Schneider et al, 2008), with superiority in resistance to disease, pest and tolerance to environmental stresses, which could be expressed in a hexaploid genetic background, as lots of related QTLs or genes had been mapped to D genome of synthetic wheat (Nkongolo et al, 1991; Innes and Kerber, 1994; Cox and Hatchett, 1994; Thompson and Haak, 1997; Yang et al, 2003; Zhu et al, 2005; Miranda et al, 2006; Ryan et al, 2010; Sohail et al, 2011; Olson et al, 2013a, 2013b; Wan et al, 2015). But the D genome of the first bread wheats were originated from only a small part of Ae.…”

“…Ae. tauschii worked as a gene repertoire for modern wheat adaptation (Jia et al, 2013; Li et al, 2014b), for their superiority in resistance to disease (Innes and Kerber, 1994; Cox et al, 1994; Yang et al, 2003; Miranda et al, 2006; Olson et al, 2013a, 2013b) and pest (Cox and Hatchett, 1994; Thompson and Haak, 1997; Zhu et al, 2005), tolerance to environmental stresses (Schachtman et al, 1991; Lan et al, 1997; Pritchard et al, 2002; Ryan et al, 2010; Sohail et al, 2011), and yield enhancement (Li et al, 2002; Huang et al, 2004; Kumar et al, 2007; Wan et al, 2015), all of which could be fixed as heterosis in hexaploid wheat theoretically.…”

Microsatellite analysis of chromosomes from the fifth homoeologous group in the introgressive Triticum aestivum/Amblyopyrum muticum wheat lines

“…The first map of 279 microsatellite loci of the wheat genome was developed in 1998 [13], and 1235 loci have already been mapped at the mean interlocus dis tance of 2.2 cM over 6 years [14]. These were now suc cessfully used in genetic studies as markers for the identification of alien chromatin introgressions into the wheat genome [15][16][17][18][19][20], relying upon their chro mosomal specificity within the wheat genome [14,21,22]. For the search of such progeny that include the 5T chromosome or its part among the diversity of wheat plants with introgressions from A. muticum, we used a microsatellite analysis at loci localized on the chromo somes of the fifth homoeologous group of wheat.…”