Molecular Mapping of Yr85 and Comparison with Other Genes for Resistance to Stripe Rust on Wheat Chromosome 1B

Introgression of tetraploid Thinopyrum elongatum 6EL segments enhances the stripe rust resistance of adult wheat plants

Preventing the widespread occurrence of stripe rust in wheat largely depends on the identification of new stripe rust resistance genes and the breeding of cultivars with durable resistance. In previous study, we reported 6E of wheat-tetraploid Thinopyrum elongatum 6E (6D) substitution line contains adult-stage stripe rust resistance genes. In this study, three novel wheat-tetraploid Th. elongatum translocation lines were generated from the offspring of a cross between common wheat and the 6E (6D) substitution line. Genomic in situ hybridization (GISH), fluorescence in situ hybridization chromosome painting (FISH painting), repetitive sequential FISH, and 55 K SNP analyses indicated that K227-48, K242-82, and K246-6 contained 42 chromosomes and were 6DL·6ES, 2DL·6EL, and 6DS·6EL translocation lines, respectively. The assessment of stripe rust resistance revealed that K227-48 was susceptible to a mixture of Pst races, whereas the 6EL lines K242-82 and K246-6 were highly resistance to stripe rust at the adult stage. Thus, this resistance was due to the chromosome arm 6EL of tetraploid Th. elongatum. The improved agronomic performance of 6DS·6EL translocation line may be a useful novel germplasm resource for wheat breeding programs. For the application of marker-assisted selection (MAS), 47 simple sequence repeat (SSR) markers were developed, showing specific amplification on the chromosome 6E using the whole-genome sequence of diploid Th. elongatum. The 6DS·6EL translocation line and SSR markers have the potential to be deploy for future stripe rust resistance wheat breeding program.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-024-01493-6.

Fine mapping of QYrsv.swust-1BL for resistance to stripe rust in durum wheat Svevo

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a serious disease that affects wheat worldwide. There is a great need to develop cultivars with combinations of all-stage resistance (ASR) and adult-plant resistance (APR) genes for sustainable control of the disease. QYrsv.swust-1BL in the Italian durum wheat (Triticum turgidum ssp. durum) cultivar Svevo is effective against Pst races in China and Israel, and the gene has been previously mapped to the long arm of chromosome 1B. The gene is flanked by SNP (single nucleotide polymorphism) markers IWB5732 and IWB4839 (0.75 cM). In the present study, we used high-density 660K SNP array genotyping and the phenotypes of 137 recombinant inbred lines (RILs) to fine map the QYrsv.swust-1BL locus within a 1.066 Mb region in durum wheat Svevo (RefSeq Rel. 1.0) on chromosome arm 1BL. The identified 1.066 Mb region overlaps with a previously described map of Yr29/QYr.ucw-1BL, a stripe rust APR gene. Twenty-five candidate genes for QYrsv.swut-1BL were identified through comparing polymorphic genes within the 1.066 Mb region in the resistant cultivar. SNP markers were selected and converted to Kompetitive allele-specific polymerase chain reaction (KASP) markers. Five KASP markers based on SNP were validated in a F2 and F2:3 breeding population, providing further compelling evidence for the significant effects of QYrsv.swut-1BL. These markers should be useful in marker-assisted selection for incorporating Yr29/QYrsv.swust-1BL into new durum and common wheat cultivars for resistance to stripe rust.

Evaluation of stripe rust resistance and genome-wide association study in wheat varieties derived from the International Center for Agricultural Research in the Dry Areas

159 wheat varieties obtained from ICARDA, CYR32, CYR33 and CYR34 were used to evaluate the stripe rust resistance in this study. Seedling resistance was carried out in the green house at the two-leaf stage. Adult-plant resistance was carried out between 2022 and 2023 in Xining and Guide, respectively. A total of 24,151 high-quality SNP loci were obtained from a 55K SNP chip data. Genome-wide association study was carried out between SNP loci and stripe rust resistance. Seedling resistance screening revealed that 91.8% (146) of wheat varieties were resistant to CYR32 and CYR33, while only 49.7% (79) of wheat varieties were resistant to CYR34. Adult-plant resistance showed 153 (96.2%) germplasms represented resistance in 2022, while only 85 (53.4%) showed resistance in 2023. An association study using the 55K SNP chip data results combined with disease ratings of 159 materials at both the seedling and adult stages discovered 593 loci related to stripe rust resistance (P ≤ 0.0001). These loci exhibited contribution rates ranging from 11.1% to 18.7%. Among them, 71 were significantly related to resistance against CYR32 at the seedling stage, with a contribution rate of 12.7%-17.2%. Constituting the vast majority, 518 loci distributed across 21 chromosomes were significantly related to CYR33 at the seedling stage, with a contribution rate of 12.6%-18.7%. Fewer loci were found to be associated with disease resistance in adult plants. In E1 environment, a sole locus was detected on chromosome 2B with a contribution rate of 14.4%. In E2 environment, however, exhibited three loci across chromosomes 2B, 4A, and 7B with contribution rates ranging from 11.1% to 16.9%. A total of 68 multi-effect loci were significantly related to resistance against both CYR32 and CYR33 at the seedling stage, and one stable locus was significantly associated with stripe rust resistance at the adult plant stage.

Development, identification, and utilization of wheat-tetraploid Thinopyrum elongatum 4EL translocation lines resistant to stripe rust

KEY MESSAGE

The new stripe rust resistance gene Yr4EL in tetraploid Th. elongatum was identified and transferred into common wheat via 4EL translocation lines. Tetraploid Thinopyrum elongatum is a valuable genetic resource for improving the resistance of wheat to diseases such as stripe rust, powdery mildew, and Fusarium head blight. We previously reported that chromosome 4E of the 4E (4D) substitution line carries all-stage stripe rust resistance genes. To optimize the utility of these genes in wheat breeding programs, we developed translocation lines by inducing chromosomal structural changes through 60Co-γ irradiation and developing monosomic substitution lines. In total, 53 plants with different 4E chromosomal structural changes were identified. Three homozygous translocation lines (T4DS·4EL, T5AL·4EL, and T3BL·4EL) and an addition translocation line (T5DS·4EL) were confirmed by the genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), FISH-painting, and wheat 55 K SNP array analyses. These four translocation lines, which contained chromosome arm 4EL, exhibited high stripe rust resistance. Thus, a resistance gene (tentatively named Yr4EL) was localized to the chromosome arm 4EL of tetraploid Th. elongatum. For the application of marker-assisted selection (MAS), 32 simple sequence repeat (SSR) markers were developed, showing specific amplification on the chromosome arm 4EL and co-segregation with Yr4EL. Furthermore, the 4DS·4EL line could be selected as a good pre-breeding line that better agronomic traits than other translocation lines. We transferred Yr4EL into three wheat cultivars SM482, CM42, and SM51, and their progenies were all resistant to stripe rust, which can be used in future wheat resistance breeding programs.

Identification of Puccinia striiformis races from the spring wheat crop in Xinjiang, China

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a foliar disease that affects both winter and spring wheat crops in Xinjiang, China, which is linked to Central Asia. Race identification of Pst from spring wheat in Xinjiang was not done before. In this study, a total of 216 isolates were recovered from stripe rust samples of spring wheat in the region in 2021 and multiplied using the susceptible cultivar Mingxian 169. These isolates were tested on the Chinese set of 19 wheat differential lines for identifying Pst races. A total of 46 races were identified. Races Suwon-11-1, Suwon11-12, and CYR32 had high frequencies in the spring wheat region. The frequencies of virulence factors on differentials "Fulhard" and "Early Premium" were high (>95%), whereas the virulence factor to differential "Triticum spelta var. Album" (Yr5) was not detected, while virulence to other differentials showed variable frequency within different counties. The predominant races in winter wheat in the same season were also detected from spring wheat cultivars, indicating Pst spreading from winter wheat to spring wheat crops. Deploying resistance genes in spring and winter wheat cultivars is critical for control stripe rust.