10.1371/journal.pone.0171963

Identification and validation of single nucleotide polymorphic markers linked to Ug99 stem rust resistance in spring wheat

Abstract

<div><p>Wheat stem rust (<i>Puccinia graminis</i> f. sp. <i>tritici</i> Eriks. and E. Henn.) is one of the most destructive diseases world-wide. Races belonging to Ug99 (or TTKSK) continue to cause crop losses in East Africa and threaten global wheat production. Developing and deploying wheat varieties with multiple race-specific genes or complex adult plant resistance is necessary to achieve durability. In the present study, we applied genome-wide association studies (GWAS) for identifying loci associated with the Ug99 stem rust resistance (SR) in a panel of wheat lines developed at the International Maize and Wheat Improvement Center (CIMMYT). Genotyping was carried out using the wheat 9K iSelect single nucleotide polymorphism (SNP) chip. Phenotyping was done in the field in Kenya by infection of <i>Puccinia graminis</i> f. sp. <i>tritici</i> race TTKST, the <i>Sr24</i>-virulent variant of Ug99. Marker-trait association identified 12 SNP markers significantly associated with resistance. Among them, 7 were mapped on five chromosomes. Markers located on chromosomes 4A and 4B overlapped with the location of the Ug99 resistance genes <i>SrND643</i> and <i>Sr37</i>, respectively. Markers identified on 7DL were collocated with <i>Sr25</i>. Additional significant markers were located in the regions where no <i>Sr</i> gene has been reported. The chromosome location for five of the SNP markers was unknown. A BLASTN search of the NCBI database using the flanking sequences of the SNPs associated with Ug99 resistance revealed that several markers were linked to plant disease resistance analogues, while others were linked to regulatory factors or metabolic enzymes. A KASP (Kompetitive Allele Specific PCR) assay was used for validating six marker loci linked to genes with resistance to Ug99. Of those, four co-segregated with the <i>Sr25</i>-pathotypes while the rest identified unknown resistance genes. With further investigation, these markers can be used for marker-assisted selection in breeding for Ug99 stem rust resistance in wheat.</p></div

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This paper was published in FigShare.

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