Introgression lines obtained from the cross between Triticum aestivumandTriticum turgidum (durum wheat) as a source of leaf and stripe (yellow)rust resistance genes

Breeding for disease resistance is a central focus of plant breeding programs, as any successful variety must have the complete package of high yield, disease resistance, agronomic performance, and end - use quality. Wheat breeding is focused on high yield, pathogen resistance and abiotic stress tolerance. Among diseases of wheat yellow rust, stem rust, and leaf rust are the most damaging diseases of wheat and other small grain cereals . Disease resistance in wheat breeding with one exception, the diseases of wheat that is important because of their effect on yield. Resistance to all diseases together can is important to avoid an unexpected loss in effectiveness of the resistance of a cu ltivar to a major disease. The genetic resistance to stem rust, leaf rust and yellow rust can be characterized as qualitative and quantitative resistances. Vertical resistance is specific to pathogen isolates based on single or very few genes. Race - specifi c is used to describe resistance that interacts differentially with pathogen races. Quantitative resistance is defined as resistance that varies in continuous way between the various phenotypes of the host population, from almost imperceptible to quite str ong. With the need to accelerate the development of improved varieties, genomics - assisted breeding is becoming an important tool in breeding programs. With marker - assisted selection, there has been success in breeding for disease resistance. Generally, bre eding programs have successfully implemented molecular markers to assist in the development of cultivars with stem, leaf and stripe rust resistance genes. When new rust resistance genes are to be deployed in wheat breeding programs, it unfortunately takes several years before the new sources of resistance will become available in commercial wheat cultivars. This is due to the long process involved in the establishment of pure breeding wheat lines. Biotechnology based techniques are available to accelerate t he breeding process via doubled haploid production.

Download Full-text

Genome-Wide Association Studies Reveal All-Stage Rust Resistance Loci in Elite Durum Wheat Genotypes

Frontiers in Plant Science ◽

10.3389/fpls.2021.640739 ◽

2021 ◽

Vol 12 ◽

Author(s):

Meriem Aoun ◽

Matthew N. Rouse ◽

James A. Kolmer ◽

Ajay Kumar ◽

Elias M. Elias

Keyword(s):

Durum Wheat ◽

Leaf Rust ◽

Stripe Rust ◽

Resistance Genes ◽

Stem Rust ◽

Rust Resistance ◽

Genome Wide Association ◽

Genome Wide ◽

Rust Pathogen ◽

Rust Resistance Genes

Leaf rust, caused by Puccinia triticina (Pt), stripe rust caused by Puccinia striiformis f. sp. tritici (Pst), and stem rust caused by Puccinia graminis f. sp. tritici (Pgt) are major diseases to wheat production globally. Host resistance is the most suitable approach to manage these fungal pathogens. We investigated the phenotypic and genotypic structure of resistance to leaf rust, stem rust, and stripe rust pathogen races at the seedling stage in a collection of advanced durum wheat breeding lines and cultivars adapted to Upper Mid-West region of the United States. Phenotypic evaluation showed that the majority of the durum wheat genotypes were susceptible to Pt isolates adapted to durum wheat, whereas all the genotypes were resistant to common wheat type-Pt isolate. The majority of genotypes were resistant to stripe rust and stem rust pathogen races. The durum panel genotyped using Illumina iSelect 90 K wheat SNP assay was used for genome-wide association mapping (GWAS). The GWAS revealed 64 marker-trait associations (MTAs) representing six leaf rust resistance loci located on chromosome arms 2AS, 2AL, 5BS, 6AL, and 6BL. Two of these loci were identified at the positions of Lr52 and Lr64 genes, whereas the remaining loci are most likely novel. A total of 46 MTAs corresponding to four loci located on chromosome arms 1BS, 5BL, and 7BL were associated with stripe rust response. None of these loci correspond to designated stripe rust resistance genes. For stem rust, a total of 260 MTAs, representing 22 loci were identified on chromosome arms 1BL, 2BL, 3AL, 3BL, 4AL, 5AL, 5BL, 6AS, 6AL, 6BL, and 7BL. Four of these loci were located at the positions of known genes/alleles (Sr7b, Sr8155B1, Sr13a, and Sr13b). The discovery of known and novel rust resistance genes and their linked SNPs will help diversify rust resistance in durum wheat.

Download Full-text

Genome-wide association mapping identifies Yellow Rust resistance locus in Ethiopian Durum Wheat germplasm

10.1101/2020.11.27.400895 ◽

2020 ◽

Author(s):

Sisay Kidane Alemu ◽

Ayele Badebo Huluka ◽

Kassahun Tesfaye Geletu ◽

Cristobal Uauy

Keyword(s):

Durum Wheat ◽

Rust Resistance ◽

Yellow Rust ◽

Genome Wide Association ◽

Lattice Design ◽

Genome Wide ◽

Population Structure Analysis ◽

Significant Difference ◽

Yellow Rust Resistance ◽

Improvement Programs

AbstractDurum wheat is an important cereal grown in Ethiopia, a country which is also its center for genetic diversity. Yellow (stripe) rust caused by Puccinia striiformis fsp tritici is one of the most devastating diseases threatening Ethiopian wheat production. To identify sources of genetic resistance to combat this pathogen, we conducted a genome wide association study of yellow rust resistance on 300 durum wheat accessions comprising 261 landraces and 39 cultivars. The accessions were evaluated for their field resistance in an alpha lattice design (10 × 30) in two replications at Meraro, Kulumsa and Chefe-Donsa in the 2015 and 2016 main growing seasons. Disease Scoring was carried out using a modified Cobb scale and then converted to Coefficient of Infection (CI). Analysis of the 35K Axiom Array genotyping data resulted in a total of 8,797 polymorphic SNPs of which 7,093 were used in subsequent analyses. Population structure analysis suggested two groups in which the cultivars clearly stood out separately from the landraces. We identified twelve SNPs significantly associated with yellow rust resistance across four chromosomes (1A, 1B, 2B, and 7B). Six of the SNPs (AX-95171339, AX-94436448, AX-95238778, AX-95096041, AX-94730403 & AX-94427201), were consistently identified on chromosome 1B at the three field locations and combined across the six environments. The phenotypic variation (R2) explained by all six SNPs on chromosome 1B ranged from 63.7 – 65.4%. Locus-based analysis of phenotypic values between resistant and susceptible allele resulted in a significant difference at (p < 0.001). Further investigation across the genomic interval encompassing the identified loci indicated the presence of disease resistance protein (NBS-LRR class) family and RPM1 in the vicinity of the loci. This study provides SNPs for tracking the QTL associated with yellow rust resistance in durum wheat improvement programs.

Download Full-text