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Fine mapping and marker development for the wheat leaf rust resistance gene Lr32
Jyoti Saini Sharma1, Curt A McCartney2, Brent D McCallum1
1Agriculture and Agri-Food Canada, Morden Research and Development Centre, Morden, MB R6M 1Y5, Canada.
G3 (Bethesda, Md.)
|October 18, 2022
Summary
Researchers developed new DNA markers for the Lr32 gene, enhancing wheat leaf rust resistance. These markers will aid in breeding wheat varieties with improved disease control against Puccinia triticina.
Area of Science:
- Plant genetics and breeding
- Agricultural pathology
- Molecular markers
Background:
- Wheat leaf rust, caused by Puccinia triticina, is a significant global threat to wheat production.
- The Lr32 gene, derived from Aegilops tauschii, offers broad-spectrum resistance but lacks modern DNA markers for breeding.
- Developing predictive DNA markers is crucial for incorporating Lr32 into elite wheat cultivars.
Purpose of the Study:
- To fine-map the Lr32 gene region on wheat chromosome 3DS.
- To develop SNP-based kompetitive allele-specific polymerase chain reaction (KASP) markers for Lr32.
- To identify candidate genes within the fine-mapped region for disease resistance.
Main Methods:
- Genomic analysis using doubled haploid and F2-derived mapping populations.
- Utilized high-density SNP arrays (90K, 35K, 820K Axiom R) and reference genomes (A. tauschii v4.0, IWGSC RefSeq v2.1).
- Developed 28 KASP and 2 simple sequence repeat (SSR) markers; fine-mapped Lr32 between KASP markers Kwh142 and Kwh355.
Main Results:
- The Lr32 region was fine-mapped to a 34-35 Mb interval on chromosome arm 3DS.
- Leaf rust resistance segregated as a Mendelian trait with 20 co-segregating markers.
- Identified 10-11 candidate disease resistance genes, primarily nucleotide-binding domain and leucine-rich repeat types, within the flanking regions.
Conclusions:
- Developed and validated two KASP markers (Kwh147 and Kwh722) for marker-assisted selection of Lr32.
- The fine-mapping and marker development facilitate the introgression of Lr32 into wheat breeding programs.
- Combining Lr32 with other resistance genes (e.g., Lr67, Lr34) can significantly enhance wheat's resistance to leaf rust.
