Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2008
Publication Date: 7/26/2008
Citation: Stoxen, S., Szabo, L.J. 2008. Assessing Population Structure of the Most Prevalent North American Races of Puccinia graminis f. sp. tritici Using Molecular Markers [abstract]. Phytopathology. 98:5152.
Technical Abstract: In the first half of the 20th century major epidemics of Puccinia graminis f. sp. tritici, the causal agent of wheat stem rust, led to significant economic loss throughout the central plains of North America. Puccinia graminis f. sp. tritici is macrocyclic, heteroecious fungus in which common barberry, the alternate host, is required for completion of the sexual life cycle. A major component of the strategy to control P. graminis f. sp. tritici has been a barberry eradication program in the United States. Without the alternate host P. graminis f. sp. tritici is predominantly an asexually population based on the repeating cycles of the dikaryotic (n+n) urediniospores. Currently this rust fungus is characterized into races, which are based on avirulence/virulence phenotypes on a standard set of 16 wheat differentials. To test if these races reflect the clonal growth of this fungus or convergent evolution simple sequence repeat (SSR) markers were used. SSR markers had previously been developed from an enriched SSR library and more recently a second set of markers has been developed from the annotated sequence available from the Pgt genome-sequencing project. Preliminary SSR data and previously examined RAPD data suggest that each race cluster forms a distinct clade and represents a single clonal lineage. The SSR markers were then used to examine phylogenetic relationships between races to test if new races arose from recombination or mutation within the existing population or from a new introduction event. Development of a standard set of genetic markers will be important for genotyping isolates of Puccinia graminis f. sp. tritici.