Abstract
Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a global concern for wheat production. Spring wheat cultivar PI 197734, of Sweden origin, has shown high-temperature adult-plant resistance (APR) to stripe rust for many years. To map resistance quantitative trait loci (QTL), 178 doubled haploid lines were developed from a cross of PI 197734 with susceptible AvS. The DH lines and parents were tested in fields in 2017 and 2018 under natural infection of Pst and genotyped with genotyping by multiplexed sequencing (GMS). Kompetitive allele specific PCR (KASP) and simple sequence repeat (SSR) markers from specific chromosomal regions were also used to genotype the population to validate and saturate resistance QTL regions. Two major QTL on chromosomes 1AL and 3BL and one minor QTL on 2AL were identified. The two major QTL, QYrPI197734.wgp-1A and QYrPI197734.wgp-3B, were detected in all tested environments explaining up to 20.7 and 46.8% phenotypic variation, respectively. An awnletted gene mapped to the expected distal end of chromosome 5AL indicated the accuracy of linkage mapping. The KASP markers converted from the GMS-SNPs in the 1A and 3B QTL regions were used to genotype 95 US spring wheat cultivars and breeding lines, and they individually showed different percentages of polymorphisms. The haplotypes of the three markers for the 1A QTL and four markers for the 3B QTL identified 37.9 and 21.1% of the wheat cultivar/breeding lines possibly carrying these two QTL, indicating their usefulness in marker-assisted selection (MAS) for incorporating the two major QTL into new wheat cultivars.
Highlights
Global wheat (Triticum aestivum L.) production is challenged by stripe rust, which is caused by fungus Puccinia striiformis Westend. f. sp. tritici Erikss. ( Puccinia striiformis f. sp. tritici (Pst))
No significant quantitative trait loci (QTL) were detected in the QTL analysis, due to the small phenotypic differences among the doubled haploid (DH) lines
These results showed the primarily additive effects of QYrPI197734.wgp-3B was closely linked with QYrMa.wgpthe resistance QTL
Summary
Global wheat (Triticum aestivum L.) production is challenged by stripe rust ( known as yellow rust), which is caused by fungus Puccinia striiformis Westend. f. sp. tritici Erikss. ( Pst). Resistance genes or quantitative trait loci (QTL) are classified into different types based on their effectiveness in different wheat growth stages and whether specific to different Pst races. All-stage resistance (ASR), called seedling resistance, is effective only against specific Pst races at all growth stages. More than 80 formally designated Yr (for yellow rust) genes and hundreds of QTL have been identified for resistance to stripe rust of wheat (Maccaferri et al, 2015; Wang and Chen, 2017; Feng et al, 2018; Nsabiyera et al, 2018; Gessese et al, 2019; Pakeerathan et al, 2019; Li et al, 2020), many of them have already lost their effectiveness. Characterization of new resistance resources is important to achieve genetic diversity for resistance among new wheat cultivars
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