Browsing by Author "Szabo, Les J"

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    Changing the Game: Using Integrative Genomics to Probe Virulence Mechanisms of the Stem Rust Pathogen Puccinia graminis f. sp. tritici
    (Frontiers in Plant Science, 2016-02-24) Steffenson, Brian; Figueroa, Melania; Upadhyaya, Narayana M; Sperschneider, Jana; Park, Robert F; Szabo, Les J; Ellis, Jeff G; Dodds, Peter N
    The recent resurgence of wheat stem rust caused by new virulent races of Puccinia graminis f. sp. tritici (Pgt) poses a threat to food security. These concerns have catalyzed an extensive global effort toward controlling this disease. Substantial research and breeding programs target the identification and introduction of new stem rust resistance (Sr) genes in cultivars for genetic protection against the disease. Such resistance genes typically encode immune receptor proteins that recognize specific components of the pathogen, known as avirulence (Avr) proteins. A significant drawback to deploying cultivars with single Sr genes is that they are often overcome by evolution of the pathogen to escape recognition through alterations in Avr genes. Thus, a key element in achieving durable rust control is the deployment of multiple effective Sr genes in combination, either through conventional breeding or transgenic approaches, to minimize the risk of resistance breakdown. In this situation, evolution of pathogen virulence would require changes in multiple Avr genes in order to bypass recognition. However, choosing the optimal Sr gene combinations to deploy is a challenge that requires detailed knowledge of the pathogen Avr genes with which they interact and the virulence phenotypes of Pgt existing in nature. Identifying specific Avr genes from Pgt will provide screening tools to enhance pathogen virulence monitoring, assess heterozygosity and propensity for mutation in pathogen populations, and confirm individual Sr gene functions in crop varieties carrying multiple effective resistance genes. Toward this goal, much progress has been made in assembling a high quality reference genome sequence for Pgt, as well as a Pan-genome encompassing variation between multiple field isolates with diverse virulence spectra. In turn this has allowed prediction of Pgt effector gene candidates based on known features of Avr genes in other plant pathogens, including the related flax rust fungus. Upregulation of gene expression in haustoria and evidence for diversifying selection are two useful parameters to identify candidate Avr genes. Recently, we have also applied machine learning approaches to agnostically predict candidate effectors. Here, we review progress in stem rust pathogenomics and approaches currently underway to identify Avr genes recognized by wheat Sr genes.
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    Puccinia coronata var. coronata , a Crown Rust Pathogen of Two Highly Invasive Species, Is Detected Across the Midwest and Northeastern United States
    (Plant Disease, 2023-07) Greatens, Nicholas; Klejeski, Nick; Szabo, Les J; Jin, Yue; Olivera, Pablo D
    Puccinia coronata var. coronata (Pcc) causes crown rust disease of glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), two highly invasive plant species in North America. Pcc is closely related to major pathogens of cereals, turfgrasses, and forage grasses. It occurs throughout Europe but was first recorded in North America in 2013. Where its hosts co-occur, such as in wetlands in the Twin Cities metro area in Minnesota, we have observed Pcc causing significant infection that results in defoliation and fruit loss in glossy buckthorns and premature leaf senescence in reed canarygrass. In this research, we mapped the distribution of this likely recently introduced rust fungus and provided a description of disease signs and symptoms and pathogen morphology. Samples were acquired by two primary means: by surveys in Minnesota and by correspondence with users of iNaturalist.org, a social network for nature enthusiasts and community scientists. With an Oxford Nanopore MinION, we sequenced two to four loci from 22 samples across 13 states and identified samples by phylogenetic analysis and sequence similarity. Notably, four pure isolates appear to have intragenomic variation of the ITS region. We found that Pcc is present throughout the range of glossy buckthorn in the eastern United States. In Minnesota, Pcc is not common outside the range of glossy buckthorn despite the presence of susceptible grass hosts.
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    SNP data of 18SPA092-1 and 25 reference isolates of the wheat stem rust fungus, Puccinia graminis f. sp. tritici
    (2022-02-04) Olivera Firpo, Pablo D; Villegas, Dolors; Cantero-Martinez, Carlos; Szabo, Les J; Rouse, Matthew N; Luster, Douglas; Bartaula, Radhika; Lopes, Marta; Jin, Yue; oliv0132@umn.edu; Olivera Firpo, Pablo D; Wheat stem rust research project / USDA-ARS Cereal Disease Laboratory and University of Minnesota
    This dataset includes 1838 SNP loci of 26 isolates of the wheat stem rust fungus, Puccina graminis f .sp. tritici. This data was used to assess the genetic relationship of a unique fungal isolate (18SPA092-1, race TKHBK) derived from a wheat stem rust sample collected in Spain in 2018 with a set of 25 reference isolates from previously defined genetic clades. Results indicate that isolate 18SPA092-1 had a unique multilocus genotype and constitutes a previously unknown lineage. Data is being released now in conjunction with publication of a primary research paper that describes this work.
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    SNP data of 56 Kazakhstani and 23 reference isolates of the wheat stem rust fungus, Puccinia graminis f. sp. tritici
    (2022-03-09) Olivera Firpo, Pablo; Szabo, Les J; Kokhmetova, Alma; Morgunov, Alexey; Luster, Douglas; Jin, Yue; oliv0132@umn.edu; Olivera Firpo, Pablo, D; Wheat stem rust research project | USDA ARS Cereal Disease Lab and University of Minnesota
    This dataset includes 2310 SNP loci of 79 isolates of the wheat stem rust fungus, Puccina graminis f .sp. tritici (Pgt). This data was used to assess the genetic diversity of a Pgt population (56 isolates) from Kazakhstan derived from stem rust samples collected in 2015-2017 wheat growing seasons. Twenty-three reference isolates from previously defined genetic clades were included in the analysis. Results indicate that the Pgt population form Kazakhstan is highly diverse and most of the isolates are of sexual origin. Data is being released now in conjunction with publication of a primary research paper that describes this work.