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

X. C. Zhang, M. C.M. Freire, M. H. Le, L. O. De Oliveira, J. W. Pitkin, G. Segers, V. C. Concibido, G. J. Baley, G. L. Hartman, G. Upchurch, K. F. Pedley, G. Stacey

Research output: Contribution to journalArticlepeer-review


Soybean rust (SBR), caused by Phakopsora pachyrhizi, is a destructive disease worldwide. Recently it has emerged as a threat to soybean production in the United States (U.S.). There is limited knowledge regarding the genetic diversity and geographic distribution of P. pachyrhizi isolates in the United States. To address this issue, a survey was conducted to define the genetic diversity and possible origin(s) of U.S. isolates. The Internal Transcribed Spacer (ITS) sequence and the ADP-Ribosylation Factor (ARF) gene sequence were amplified and cloned from a collection of 59 isolates. Consequently, the cloned ITS and ARF sequences were subject to phylogenetic analyses. At least five genotypes were identified within the U.S. isolates and most states contained a mixture of isolates. Gauged by the DNA sequences derived from international and archival isolates, two groups of global isolates that are endemic to all continents were identified. This reinforces the hypothesis of a global migration of P. pachyrhizi. However, there are also two groups of isolates that appeared to be present only in Asia, Australia and U.S. This suggests the presence of a possible alternative migratory pathway. One isolate type appeared to be unique to the U.S., suggesting either a unique origin or rapid diversification of isolates collected from the U.S. The data provide the most comprehensive analysis to date of the genetic diversity of P. pachyrhizi isolates in the U.S.

Original languageEnglish (US)
Pages (from-to)52-65
Number of pages14
JournalAsian Journal of Plant Pathology
Issue number3
StatePublished - 2012


  • Genetic diversity
  • Phakopsora pachyrhizi
  • Phylogeographic distribution
  • Soybean breeding
  • Soybean rust

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science
  • Horticulture


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