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POSTERS: Late Breaking II

P-664 - Genomic analyses of a sexually recombining population of the wheat stem rust pathogen from Spain reveals effector diversity & novel avirulence loci

Tuesday, August 5, 2025
10:15 AM - 11:00 AM HST
Location: Exhibit Hall 3

    Presenting author(s)

  • MV

    Molly Veregge

    Graduate Student
    University of Minnesota
    St Paul, Minnesota, United States

    • Author(s)

  • DV

    Dolors Villegas

    Department of Genetics & Plant Breeding, Estacion Experimental de Aula Dei, CSIC
    Zaragoza, Aragon, Spain

  • CC

    Carlos Cantero-Martinez

    Agricultural and Forest Sciences and Engineering Department, University of Lleida, Agrotecnio Center
    Lleida, Catalonia, Spain

  • MC

    Melissa Carter

    USDA-ARS Foreign Disease-Weed Science Research Unit
    Ft. Detrick, Maryland, United States

  • DL

    Doug Luster

    Research Plant Physiologist
    USDA-ARS-NEA, Foreign Disease-Weed Science Research Unit
    Fort Detrick, Maryland, United States

  • MM

    Matthew Moscou

    Research Plant Pathologist
    USDA ARS Cereal Disease Laboratory
    St Paul, Minnesota, United States

  • YJ

    Yue Jin

    USDA ARS Cereal Disease Laboratory
    St Paul, Minnesota, United States

  • PO

    Pablo Olivero-Firpo

    Research Plant Pathologist
    USDA ARS Cereal Disease Laboratory
    St Paul, Minnesota, United States

Abstract Text:

Puccinia graminis f. sp. tritici (Pgt), the causal agent of wheat stem rust, has historically caused devastating epidemics. In the 20th century, barberry eradication programs in the United States and Europe curbed disease by removing the sexual stage of the pathogen’s life cycle, limiting the emergence of new virulent races. However, the resurgence of common barberry in Europe has resulted in renewed outbreaks of wheat stem rust where it has been nearly absent for over 50 years. We characterized a Pgt population of sexual origin derived from native barberry and adjacent wheat samples collected in 2019 in Spain. This diverse population of 200 unique races exhibit novel and significant virulence combinations, including on Ug99-effective genes, and on Sr31, a trait only seen in races of the Ug99 group. Whole-genome Illumina sequencing of 153 isolates segregating on 18 stem rust resistance genes reveled high genetic diversity. We identified 14 novel alleles of cloned Pgt effectors to be functionally validated. Additionally, genome-wide association studies identified loci containing putative effector genes corresponding to the stem rust resistance genes Sr21 and Sr5. Ongoing work aims to clone and functionally validate these candidate avirulence genes. This highly diverse sexually recombining population is leading to the discovery of relevant avirulence loci, providing valuable insight into the evolution of Pgt virulence.