Location: Cereal Disease Lab
Project Number: 5062-21220-025-023-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jul 1, 2023
End Date: Jan 31, 2026
Objective:
The objectives are to: 1) Maintain and strengthen the existing wheat stem rust diagnostic network to detect and track pathogen changes and movements across the target regions (East Africa and South Asia), using a combination of pathotyping and genotyping methods; and 2) Collect and collate data on host resistance (wheat genes for stem rust resistance), integrate with pathogen data to permit better vulnerability and risk assessments and enable disease control scenario modelling.
Approach:
Wheat stem rust pathogen pathotyping activities will include: 1) Deriving pure isolates from stem rust samples; 2) Determining races based on rust reactions of the North American differential set through inoculation experiments; and 3) Characterizing isolates against additional Sr genes that are important in current/anticipatory breeding. Genotyping activities for living and dead ("d-samples") stem rust samples received from East Africa and South Asia include: 1) Determining defined major clades and race groups based on a core assay of 17 SNPs to enable time-sensitive Pgt clade and race group identification; 2) Defining new clades/MLGs if isolates/samples are out of the known clades; and 3) Genotyping selected isolates with significant and novel virulences with 3.0K SNP chip.
The wheat stem rust pathogen will also be monitoring on the alternate hosts (Barberry/Mahonia). Alternate host monitoring activities include: 1) Surveying barberry and mahonia species that are closely associated with wheat production in East Africa and South Asia; 2) Collecting aecial infections on alternate hosts and determining rust species/forms based on reactions of the cereals identification series in combination with DNA analysis; 3) Deriving pure isolates of respective rust species, and 4) Determining races (or racetyping) based on rust reactions of differentials through inoculation experiments.
Wheat stem rust resistance seedling screening and marker assays will be used to determine the likely resistance present in varieties being grown in the target regions. Seedling screening will be undertaken using important stem rust races under controlled greenhouse conditions at the USDA, ARS. Molecular markers would also be used to assess important Sr genes (Sr2, Sr7a, Sr12, Sr13, Sr22, Sr24, Sr25, Sr26, Sr31, Sr33, Sr38, Sr50, Sr57(Lr34), Sr1RSAmigo, and Sr8155B1) in current cultivars and breeding germplasm. The primary focus would be screening of the major cultivars currently being grown in the target regions. At the start of the project, attempts would be made to source seed of major cultivars from partner countries.
