Pathotype Complexity and Genetic Characterization of Phytophthora sojae Populations in Illinois, Indiana, Kentucky, and Ohio

Linda M. Hebb, Carl A. Bradley, Santiago Xavier Mideros, Darcy E.P. Telenko, Kiersten Wise, Anne E. Dorrance

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Phytophthora sojae, the causal agent of Phytophthora root and stem rot of soybean, has been managed with single Rps genes since the 1960s but has subsequently adapted to many of these resistance genes, rendering them ineffective. The objective of this study was to examine the pathotype and genetic diversity of P. sojae from soil samples across Illinois, Indiana, Kentucky, and Ohio by assessing which Rps genes were still effective and identifying possible population clusters. There were 218 pathotypes identified from 473 P. sojae isolates with an average of 6.7 out of 15 differential soybean lines exhibiting a susceptible response for each isolate. Genetic characterization of 103 P. sojae isolates from across Illinois, Indiana, Kentucky, and Ohio with 19 simple sequence repeat markers identified 92 multilocus genotypes. There was a moderate level of population differentiation between these four states, with pairwise FST values ranging from 0.026 to 0.246. There were also moderate to high levels of differentiation between fields, with pairwise FST values ranging from 0.071 to 0.537. Additionally, cluster analysis detected the presence of P. sojae population structure across neighboring states. The level of pathotype and genetic diversity, in addition to the identification of population clusters, supports the hypothesis of occasional outcrossing events that allow an increase in diversity and the potential to select for a loss in avirulence to specific resistance genes within regions. The trend of suspected gene flow among neighboring fields is expected to be an ongoing issue with current agricultural practices.

Original languageEnglish
Pages (from-to)663-681
Number of pages19
JournalPhytopathology
Volume112
Issue number3
DOIs
StatePublished - Mar 2022

Bibliographical note

Funding Information:
Funding: Support was provided by Purdue University; the North Central Soybean Research Program; the Ohio Soybean Council; the University of Kentucky; the College of Agricultural, Consumer and Environmental Sciences, University of Illinois at Urbana–Champaign; the Kentucky Soybean Promotion Board; and the Ohio Agricultural Research and Development Center, Ohio State University.

Publisher Copyright:
© 2022 The American Phytopathological Society

Keywords

  • Phytophthora root and stem rot
  • Phytophthora sojae
  • Rps genes
  • genetics and resistance
  • population biology
  • population genetics
  • simple sequence repeat
  • soybean

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science

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