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United States Department of Agriculture

Agricultural Research Service

Research Project: SOYBEAN DISEASE AND PEST MANAGEMENT

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

Title: Genetic diversity and origins of Phakopsora pachyrhizi isolates in the United States

Authors
item Zhang, Xue-Cheng -
item Freire, Maira C.M. -
item Le, Mi Ha -
item Hartman, Glen
item Upchurch, Robert
item Pedley, Kerry
item Stacey, Gary -

Submitted to: Asian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 28, 2012
Publication Date: December 3, 2012
Citation: Zhang, X., Freire, M., Le, M., Hartman, G.L., Upchurch, R.G., Pedley, K.F., Stacey, G. 2012. Genetic diversity and origins of Phakopsora pachyrhizi isolates in the United States. Asian Journal of Plant Pathology. 6:52-65.

Interpretive Summary: Soybean rust (SBR) is a fungal disease of worldwide concern. There is limited knowledge about the genetic population structure of Phakopsora pachyrhizi isolates in the United States. To address this issue, a survey was conducted to define the genetic diversity and possible origins of US isolates. At least five distinct isolate types within the US were identified and most states contained a mixture of isolates. Gauged by sequences from international and archival isolates, we identified two groups of global isolates that are endemic to all continents, reinforcing the hypothesis of a global migration of P. pachyrhizi. However, we also identified a few groups that appeared to be present only in Asia, Australia, and North America, suggesting the presence of a possible alternative migratory pathway. Interestingly, one isolate type appears to be unique to the United States, suggesting either a unique origin or very rapid diversification of isolates in North America. The data provide the most comprehensive analysis to date of the genetic diversity of P. pachyrhizi isolates in North America. This information will be useful to plant pathologists interested in knowing more about molecular variability of the soybean rust pathogen.

Technical Abstract: Soybean rust (SBR) is a destructive disease worldwide and is a newly emerged threat to soybean production in the United States. Although deployment of resistant germplasm is the most preferred means of disease control, there is limited knowledge about the population structure of Phakopsora pachyrhizi isolates in the US. To address this issue, a survey was conducted to define the genetic diversity and possible origins of US isolates. At least five distinct isolate types within the US were identified and most States contained a mixture of isolates. Gauged by sequences from international and archival isolates, we identified two groups of global isolates that are endemic to all continents, reinforcing the hypothesis of a global migration of P. pachyrhizi. However, we also identified a few groups that appeared to be present only in Asia, Australia, and North America, suggesting the presence of a possible alternative migratory pathway. Interestingly, one isolate type appears to be unique to the United States, suggesting either a unique origin or very rapid diversification of isolates in North America. The data provide the most comprehensive analysis to date of the genetic diversity of P. pachyrhizi isolates in North America.

Last Modified: 8/27/2014
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