Organizing Committee


Poster Presentations

Poster Presentations


Virulence diversity in Phakopsora pachyrhizi isolates collected in the United States

Presenter: M. Twizeyimana

All authors and affiliations: M. TWIZEYIMANA (1), G. L. Hartman (2). (1) Department of Crop Sciences, University of Illinois at Urbana-Champaign, IL; (2) USDA-ARS and Department of Crop Sciences, University of Illinois, Urbana, IL

Phakopsora pachyrhizi, the cause of soybean rust, is known to limit soybean yields under favorable conditions conducive to rust development. The pathogen has become established in most southern U.S. locations bordering the Gulf of Mexico where kudzu overwinters. To determine the virulence diversity in U.S. P. pachyrhizi isolates, infected soybean and kudzu leaf samples were collected from multiple locations in 12 states (Alabama, Arkansas, Florida, Georgia, Illinois, Louisiana, Mississippi, Oklahoma, North Carolina, South Carolina, Texas, and Virginia). From all samples collected, a total of 62 single spore isolates was successfully established and included 4, 24, and 34 isolates collected in 2006, 2007, and 2008, respectively. Forty isolates were obtained from soybean, whereas 22 were from kudzu. A putative host differential set, composed of five accessions containing Rpp1, Rpp2, Rpp3, Rpp4, Rpp5, and Hyuuga genes for resistance to P. pachyrhizi and one highly resistant (UG-5) and two highly susceptible cultivars (Williams 82, TGx 1485-1D), was selected for the virulence diversity study. Principal component and cluster analyses on the reaction type and the number of uredinia per cm2 of leaf tissue separated the rust isolates into clusters. Along with this virulence diversity, the genetic diversity of the same isolates is being studied using simple sequence repeat markers to determine the relationship between pathogen variation and genetic variation.

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