The genetic structure of Pseudoperonospora cubensis global populations
L. QUESADA-OCAMPO (1), L. Granke (1), J. Olsen (1), H. Gutting (1), F. Runge (2), M. Thines (2), A. Lebeda (3), M. Hausbeck (1)
(1) Michigan State University, East Lansing, MI, U.S.A.; (2) University of Hohenheim, Hohenheim, GERMANY; (3) Palacky University in Olomouc, Faculty of Science, Department of Botany, Olomouc-Holice, CZECH REPUBLIC
Phytopathology 101:S149

Pseudoperonospora cubensis is a destructive foliar pathogen that infects economically important Cucurbitaceous crops in the United States and worldwide. In this study, we investigated the genetic structure of 465 P. cubensis isolates from three continents, 13 countries, 19 U.S. states, five host species and spanning 28 years. Isolates were assigned to predefined host, geographic and year categories and genotyped for two mitochondrial and five nuclear loci. Bayesian clustering resolved six genetic clusters and suggested some population structure by geographic origin and host, as some clusters occurred more or less frequently in particular categories. Since genetic structuring was detected in P. cubensis populations, it is important to include isolates that represent the genetic variation in P. cubensis when developing diagnostic tools, fungicides, and resistant host varieties. The population structure detected should also be taken into account when designing and interpreting association studies in this pathogen. While this study provides an initial map of global population structure of P. cubensis, it highlights the need of an assembled genome to generate single-copy markers for evolutionary and populations studies. Future genotyping of additional isolates would be useful to determine population structure within specific geographic regions or across a wider range of hosts.