| 1. |
- Ashraf, Rimsha
(författare)
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Determination, characterisation and combination of novel resistance genes to stripe and stem rust in wheat
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Triticum aestivum L., commonly known as bread wheat, characterized by a chromosomal composition of 2n = 6x = 42 (AABBDD), is a significant source of dietary protein and daily calorie intake for much of the global population. Stripe rust (Puccinia striiformis Westend. f. sp. tritici Eriks) and stem rust (Puccinia graminis f. sp. tritici Erikss & E. Henning) now pose substantial threats to overall wheat production worldwide, since most rust resistance genes in wheat have been overcome by virulent rust fungus races. It is essential to enhance genetic resistance against these devastating diseases.Wheat acquires crucial reservoirs of new resistance genes through introgressions from derivatives of Secale cereale, Leymus mollis, Leymus racemosus, and Thinopyrum junceiforme. This study systematically examined seedling resistance to various stripe rust races to identify new sources of resistance. Six wheat-rye introgression lines (SLU124, SLU125, SLU126, SLU127, SLU128 and SLU129) containing rye chromosomes 4R, 5R, and 6R were identified as carriers of previously undiscovered resistance genes against stripe rust races. Seedling assays confirmed that the stripe rust resistance in line SLU126 was retained over multiple generations. Using genotyping-by-sequencing (GBS) platforms and aligning putative GBS-SNPs with fully annotated rye NLR genes, three Kompetitive Allele-Specific PCR (KASP) markers were designed specifically for a chromosomal region at chromosome 6R, associated with two distinct stripe rust resistance genes. The development and validation of the wheat-rye cryptic translocation 6DS.6DL.6RL.6DL, featuring newfound stripe rust resistance genes, were conducted through seedling resistance assays and molecular analysis. The stripe rust resistance gene in family 29-N3-5 onthe rye chromosome 6RL arm was provisionally designated YrSLU. Extensive molecular marker analysis and multiple-generation seedling assays revealed that stripe rust resistance in SLU124 is located on the 4RL chromosome arm of rye. Two KASP markers located on the 4RL chromosome were identified as being closely associated with two stripe rust resistance genes in resistant plants of a SLU124 population. Using marker-assisted gene pyramiding, stem rust resistance gene Sr59 and stripe rust resistance gene YrSLU were combined in a single wheat genotype.Overall, this thesis demonstrated the advantages of marker-assisted gene pyramiding in transferring multiple disease resistance genes within a single genotype. Incorporation of these resistance genes into wheat has expanded the gene pool for combating destructive diseases.
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| 2. |
- Ashraf, Rimsha, et al.
(författare)
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Identification of a Small Translocation from 6R Possessing Stripe Rust Resistance to Wheat
- 2023
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Ingår i: Plant Disease. - 0191-2917 .- 1943-7692. ; 107, s. 720-729
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Tidskriftsartikel (refereegranskat)abstract
- Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici Eriks. & E. Henn, is the most devastating fungal disease of bread wheat. Here, a wheat-rye multiple disomic substitution line, SLU126 4R (4D), 5R (5D), and 6R (7D), possessing resistance against 25 races of P. striiformis f. sp. tritici, was used and crossed with Chinese Spring ph1b to induce homeologous recombination to produce introgressions with a reduced rye chromosome segment. Seedling assays confirmed that the stripe rust resistance from SLU126 was retained over multiple generations. Through genotyping-by-sequencing (GBS) platforms and aligning the putative GBS-single-nucleotide polymorphism (SNPs) to the full-length annotated rye nucleotide-binding leucine-rich repeat (NLR) genes in the parental lines (CS ph1b, SLU126, CSA, and SLU820), we identified the physical position of 26, 13, and 9 NLR genes on chromosomes 6R, 4R, and 5R, respectively. The physical positions of 25 NLR genes on chromosome 6R were identified from 568,460,437 bp to 879,958,268 bp in the 6RL chromosome segment. Based on these NLR positions on the 6RL chromosome segment, the three linked SNPs (868,123,650 to 873,285,112 bp) were validated through kompetitive allele-specific PCR (KASP) assays in SLU126 and resistance plants in the family 29-N3-5. Using these KASP markers, we identified a small piece of the rye translocation (i.e., as a possible 6DS.6DL.6RL.6DL) containing the stripe resistance gene, temporary designated YrSLU, within the 6RL segment. This new stripe rust resistance gene provides an additional asset for wheat improvement to mitigate yield losses caused by stripe rust.
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| 3. |
- Ashraf, Rimsha
(författare)
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Utilization of wheat relatives to improve wheat breeding for rust resistance
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Wheat is a major food source in a range of countries, thereby largely contributing to food security in vast areas worldwide. Stripe rust (Puccinia striiformis f. sp. tritici), stem rust (P. graminis f. sp. tritici) and leaf rust (P. triticina erikson) are three major wheat diseases which cause yield and quality loss of wheat. Wild relatives of wheat are dynamic resources for unique traits, not present in cultivated wheat. Different breeding strategies have been used for introgression of alien genes into wheat, to transfer genes contributing tolerance/resistance against biotic and abiotic stresses. The secondary and tertiary gene pools are playing a pivotal role in developing wheat-alien introgression lines. In this paper, the importance of wheat, types of rust, rust resistance types, wheat gene pools, molecular methods used for gene deployment and utilization of alien germplasm are discussed.
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| 4. |
- Johansson, Eva, et al.
(författare)
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Diverse Wheat-Alien Introgression Lines as a Basis for Durable Resistance and Quality Characteristics in Bread Wheat
- 2020
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Wheat productivity has been significantly improved worldwide through the incorporation of novel genes from various gene pools, not least from wild relatives of wheat, into the commonly cultivated bread and durum wheat. Here, we present and summarize results obtained from a diverse set of wheat-alien introgression lines with mainly introgressions of rye, but also ofLeymusspp. andThinopyrum junceiformeinto bread-wheat (Triticum aestivumL.). From this material, lines carrying 2RL were found with good agronomic performance and multiple resistance not least towards several races of powdery mildew. A novel resistance gene, one of few showing resistance towards all today identified stem rust races, designatedSr59, was also found originating from 2RL. Lines with multiple introgressions from 4R, 5R, and 6R were found resistant towards the majority of the stripe rust races known today. Due to lack of agricultural adaptation in these lines, transfer of useful genes into more adapted wheat material is a necessity, work which is also in progress through crosses with the CSph1bmutant, to be able to only transfer small chromosome segments that carry the target gene. Furthermore, resistance towards Russian wheat aphid was found in lines having a substitution of 1R (1D) and translocations of 3DL.3RS and 5AL.5RS. The rye chromosomes 1R, 2R, and 6R were found responsible for resistance towards the Syrian Hessian fly. High levels of especially zinc was found in several lines obtained from crosses withLeymus racemosusandLeymus mollis, while also some lines with 1R, 2R, or 5R showed increased levels of minerals and in particular of iron and zinc. Moreover, lines with 1R, 2R, 3R, andLeymusspp. introgressions were also found to have a combination of high iron and zinc and low cadmium concentrations. High variation was found both in grain protein concentration and gluten strength, measured as %UPP, within the lines, indicating large variation in bread-making quality. Thus, our study emphasizes the impact that wheat-alien introgression lines can contribute to current wheat lines and shows large opportunities both to improve production, resistance, and quality. To obtain such improvements, novel plant breeding tools, as discussed in this paper, opens unique opportunities, to transfer suitable genes into the modern and adapted wheat cultivars.
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