title: The Irish potato famine pathogen Phytophthora infestans originated in central Mexico rather than the Andes.
abstract: Phytophthora infestans is a destructive plant pathogen best known for causing the disease that triggered the Irish potato famine and remains the most costly potato pathogen to manage worldwide. Identification of P. infestan's elusive center of origin is critical to understanding the mechanisms of repeated global emergence of this pathogen. There are two competing theories, placing the origin in either South America or in central Mexico, both of which are centers of diversity of Solanum host plants. To test these competing hypotheses, we conducted detailed phylogeographic and approximate Bayesian computation analyses, which are suitable approaches to unraveling complex demographic histories. Our analyses used microsatellite markers and sequences of four nuclear genes sampled from populations in the Andes, Mexico, and elsewhere. To infer the ancestral state, we included the closest known relatives Phytophthora phaseoli, Phytophthora mirabilis, and Phytophthora ipomoeae, as well as the interspecific hybrid Phytophthora andina. We did not find support for an Andean origin of P. infestans; rather, the sequence data suggest a Mexican origin. Our findings support the hypothesis that populations found in the Andes are descendants of the Mexican populations and reconcile previous findings of ancestral variation in the Andes. Although centers of origin are well documented as centers of evolution and diversity for numerous crop plants, the number of plant pathogens with a known geographic origin are limited. This work has important implications for our understanding of the coevolution of hosts and pathogens, as well as the harnessing of plant disease resistance to manage late blight.
authors.affiliation: Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611;
authors.forename: Erica M
authors.initials: EM
authors.lastname: Goss
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331;
authors.forename: Javier F
authors.initials: JF
authors.lastname: Tabima
authors.affiliation: The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland;
authors.forename: David E L
authors.initials: DE
authors.lastname: Cooke
authors.affiliation: Department of Biological Sciences, University of the Andes, 110321 Bogota, Colombia;
authors.forename: Silvia
authors.initials: S
authors.lastname: Restrepo
authors.affiliation: Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853;
authors.forename: William E
authors.initials: WE
authors.lastname: Fry
authors.affiliation: CIP China Center for Asia and the Pacific, International Potato Center, Beijing 100081, China;
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Forbes
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331;
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Fieland
authors.affiliation: Department of Biological Sciences, University of the Andes, 110321 Bogota, Colombia;
authors.forename: Martha
authors.initials: M
authors.lastname: Cardenas
authors.affiliation: Horticultural Crops Research Laboratory, US Department of Agriculture Agricultural Research Service, Corvallis, OR 97330; andDepartment of Botany and Plant Pathology and Center for Genome Biology and Biocomputing, Oregon State University, Corvallis, OR 97331 grunwaln@science.oregonstate.edu.
authors.forename: Niklaus J
authors.initials: NJ
authors.lastname: Grünwald
mesh_terms: D000465:Algorithms; D001499:Bayes Theorem; D003105:Colombia; D004484:Ecuador; D019143:Evolution, Molecular; D005838:Genotype; D005843:Geography; D049672:History, 19th Century; D006801:Humans; D007494:Ireland; D008800:Mexico; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D010568:Peru; D010802:Phylogeny; D055750:Phytophthora infestans / Q000235:genetics*; D010935:Plant Diseases / Q000266:history; D025341:Principal Component Analysis; D011198:Solanum tuberosum / Q000469:parasitology*; D013217:Starvation / Q000266:history
keywords: biological invasion; coalescent analysis; oomycete; population genetics; stramenopile