Abstract
The Chinese wheat landrace “Gaoxianguangtoumai” (GX) has exhibited a high level of adult-plant resistance (APR) to stripe rust in the field for more than a decade. To reveal the genetic background for APR to stripe rust in GX, a set of 249 F6:8 (F6, F7, and F8) recombinant inbred lines (RILs) was developed from a cross between GX and the susceptible cultivar “Taichung 29.” The parents and RILs were evaluated for disease severity at the adult-plant stage in the field by artificial inoculation with the currently predominant Chinese Puccinia striiformis f. sp. tritici races during three cropping seasons and genotyped using the Wheat 55K single-nucleotide polymorphism (SNP) array to construct a genetic map with 1,871 SNP markers finally. Two stable APR quantitative trait loci (QTL), QYr.GX-2AS and QYr.GX-7DS in GX, were detected on chromosomes 2AS and 7DS, which explained 15.5–27.0% and 11.5–13.5% of the total phenotypic variation, respectively. Compared with published Yr genes and QTL, QYr.GX-7DS and Yr18 may be the same, whereas QYr.GX-2AS is likely to be novel. Haplotype analysis revealed that QYr.GX-2AS is likely to be rare which presents in 5.3% of the 325 surveyed Chinese wheat landraces. By analyzing a heterogeneous inbred family (HIF) population from a residual heterozygous plant in an F8 generation of RIL, QYr.GX-2AS was further flanked by KP2A_36.85 and KP2A_38.22 with a physical distance of about 1.37Mb and co-segregated with the KP2A_37.09. Furthermore, three tightly linked Kompetitive allele-specific PCR (KASP) markers were highly polymorphic among 109 Chinese wheat cultivars. The results of this study can be used in wheat breeding for improving resistance to stripe rust.
Highlights
Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is among the most harmful and widespread obligate pathogens of common wheat (Triticum aestivum L.) worldwide (Knott, 1989; Wellings, 2011)
GX-7DS could be significantly detected in two field trials and Busing the ICIM-EPI functionality of the quantitative trait loci (QTL) IciMapping v4.2 (Supplementary Table S4). These results indicated that the highlevel resistance in GX was contributed by these two QTL through additive and epistatic interactions, where QYr.GX-2AS provided relatively stronger resistance to Pst races than QYr.GX-7DS
A large number of genes or QTL that confer various degrees of adult-plant resistance (APR) to stripe rust have been identified (Chen, 2013), but most only have minor effects on stripe rust response and are difficult to use in breeding
Summary
Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is among the most harmful and widespread obligate pathogens of common wheat (Triticum aestivum L.) worldwide (Knott, 1989; Wellings, 2011). In China, stripe rust prevailed for several times in large wheat-growing areas and this caused serious yield losses (Zeng and Luo, 2006; Chen et al, 2014; Han and Kang, 2018). Since the 1950s, four severe epidemics of wheat stripe rust have occurred in China in 1950, 1964, 1990, and 2002, resulting in yield losses of 6.0, 3.2, 1.8, and 1.4 million tonnes, respectively (Li and Zeng, 2000; Wan et al, 2004). The main cause of the outbreaks is the emergence of new virulent races that overcome the widely deployed resistance genes (Chen and Kang, 2017). New virulent Pst race CYR34 appears and overcomes the widely deployed Yr genes. Continuous improvement in the resistance of wheat cultivars to cope with evolving races of Pst is a high priority to control stripe rust (Manickavelu et al, 2016)
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