Research Project: Surveillance, Pathogen Biology, and Host Resistance of Cereal Rusts

Location: Cereal Disease Lab

Project Number: 5062-21220-025-000-D
Project Type: In-House Appropriated

Start Date: Mar 28, 2022
End Date: Mar 27, 2027

Objective:
Objective 1: Monitor, collect, and characterize U.S. cereal rust pathogen populations, and characterize foreign populations that threaten U.S. cereal production. • Sub-objective 1.A: Monitor, collect and characterize cereal rust pathogen populations in the U.S. for virulence that overcomes rust resistance genes in current cultivars. • Sub-objective 1.B: Characterize key exotic rust pathogen strains in advance of their introduction to the United States and contribute towards consortia for global pathogen surveillance through strategic partnerships and alliances. • Sub-objective 1.C: Development and/or improvement of molecular diagnostic tools for detection of cereal rust pathogen strains. Objective 2: Develop new genomic resources for cereal rust pathogens, identify links between pathogen phenotypes and genotypes, and improve understanding of the role of the sexual cycle in population dynamics. • Sub-objective 2.A: Develop genomic resources for population genetics and evolutionary studies of cereal rust pathogens. • Sub-objective 2.B: Identify linkages between phenotype and genotype of cereal rust fungi involved in pathogenicity and host resistance. • Sub-objective 2.C: Improve understanding of the roles of the sexual cycle in cereal rust fungal population dynamics. Objective 3: Improve host resistance in cereal crops to rust pathogens through investigations in sources and genetics of rust resistance, characterization of various germplasm, and incorporation into adapted germplasm. • Sub-objective 3.A: Evaluate wheat, oat and barley germplasm from U.S. breeding programs for rust resistance. • Sub-objective 3.B: Identify and characterize new sources of rust resistance in wheat, barley, and oat. • Sub-objective 3.C: Incorporate rust resistance into adapted germplasm.

Approach:
Cereal rust fungi are dynamic leading to constant changes in the U.S. populations, which leads to the erosion of effective resistance in cereal crops. In addition, foreign isolates further threaten cereal production if they are introduced and established. Development of cereal cultivars with effective rust resistance will depend on the monitoring and characterization of virulence phenotypes of the rust pathogens with host differential lines containing single genes for rust resistance. Rust fungi have large, complex genomes and the uredinial stage is dikaryotic with two distinct haploid genomes. Genetic and genomic approaches will be used to (1) complete phased haploid genome assemblies for cereal rust fungi; (2) characterize population genetics of cereal rust pathogens; and (3) identify linkages between phenotype and genotype of cereal rust fungi involved in pathogenicity and host resistance. Surveys and identification of rust infections on Berberis and Mahonia species will be conducted to investigate the potential roles of alternate hosts in pathogen variations and disease epidemiology. Rust resistant cereal germplasm will be selected by testing wheat, oat, and barley lines from breeding programs throughout the U.S. for resistance to Pca, Pgt, P. hordei and P. triticina, using prevalent races, and races that have high virulence to rust resistance genes common in released cultivars and breeding lines. The identity of rust resistance genes in breeding lines will be postulated in seedling tests using specific races of these rust fungi. Adult plant resistance of breeding lines will be evaluated in field plots. Genetic loci that mediate rust resistance genes will be identified along with molecular markers that facilitate plant breeding via marker assisted selection. Advanced germplasm lines with combinations of rust resistance genes will be derived and distributed for use in cultivar development.