Stripe rust (caused by Puccinia striiformis f. sp. tritici) is one of the most severe diseases affecting wheat production. The disease is best controlled by developing and growing resistant cultivars. Chinese wheat (Triticum aestivum) landraces have excellent resistance to stripe rust. The objectives of this study were to identify wheat landraces with stable resistance and map quantitative trait loci (QTL) for resistance to stripe rust from 271 Chinese wheat landraces using a genome-wide association study (GWAS) approach. The landraces were phenotyped for stripe rust responses at the seedling stage with two predominant Chinese races of P. striiformis f. sp. tritici in a greenhouse and the adult-plant stage in four field environments and genotyped using the 660K wheat single-nucleotide polymorphism (SNP) array. Thirteen landraces with stable resistance were identified, and 17 QTL, including eight associated to all-stage resistance and nine to adult-plant resistance, were mapped on chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 5A, 5B, 6D, and 7A. These QTL explained 6.06–16.46% of the phenotypic variation. Five of the QTL, QYrCL.sicau-3AL, QYrCL.sicau-3B.4, QYrCL.sicau-3B.5, QYrCL.sicau-5AL.1 and QYrCL.sicau-7AL, were likely new. Five Kompetitive allele specific PCR (KASP) markers for four of the QTL were converted from the significant SNP markers. The identified wheat landraces with stable resistance to stripe rust, significant QTL, and KASP markers should be useful for breeding wheat cultivars with durable resistance to stripe rust.
Chinese wheat landrace Anyuehong (AYH) has displayed high levels of stable adult-plant resistance (APR) to stripe rust for more than 15 years. To identify QTL for stripe rust resistance in AYH, a set of 110 recombinant inbred lines (RILs) was developed from a cross between AYH and susceptible cultivar Taichung 29. The parents and RILs were evaluated for final disease severity (FDS) in six field tests with a mixture of predominant Pst races at the adult-plant stage and genotyped using the wheat 55K SNP array to construct a genetic map with 1,143 SNP markers. Three QTL, designated as QYr.AYH-1AS, QYr.AYH-5BL and QYr.AYH-7DS, were mapped on chromosome 1AS, 5BL and 7DS, respectively. RILs combining three QTL showed significantly reduced FDS compared with the lines in other combinations. Of them, QYr.AYH-5BL and QYr.AYH-7DS were stably detected in all environments, explaining 13.6–21.4% and 17.6–33.6% of phenotypic variation, respectively. Compared with previous studies, QYr.AYH-5BL may be a new QTL, while QYr.AYH-7DS may be Yr18. Haplotype analysis revealed that QYr.AYH-5BL is likely present in 6.2% of the 323 surveyed Chinese wheat landraces. The Kompetitive allele specific PCR (KASP) markers for QYr.AYH-5BL were developed by the linked SNP markers to successfully confirm the effects of the QTL in a validation population derived from a residual heterozygous line, and were further assessed in 38 Chinese wheat landraces and 92 cultivars. Our results indicated that QYr.AYH-5BL with linked KASP markers should have potential value for marker-assisted selection to improve stripe rust resistance in breeding programs.
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