title: High levels of diversity and population structure in the potato late blight pathogen at the Mexico centre of origin.
abstract: Globally destructive crop pathogens often emerge by migrating out of their native ranges. These pathogens are often diverse at their centre of origin and may exhibit adaptive variation in the invaded range via multiple introductions from different source populations. However, source populations are generally unidentified or poorly studied compared to invasive populations. Phytophthora infestans, the causal agent of late blight, is one of the most costly pathogens of potato and tomato worldwide. Mexico is the centre of origin and diversity of P. infestans and migration events out of Mexico have enormously impacted disease dynamics in North America and Europe. The debate over the origin of the pathogen, and population studies of P. infestans in Mexico, has focused on the Toluca Valley, whereas neighbouring regions have been little studied. We examined the population structure of P. infestans across central Mexico, including samples from Michoacán, Tlaxcala and Toluca. We found high levels of diversity consistent with sexual reproduction in Michoacán and Tlaxcala and population subdivision that was strongly associated with geographic region. We determined that population structure in central Mexico has contributed to diversity in introduced populations based on relatedness of U.S. clonal lineages to Mexican isolates from different regions. Our results suggest that P. infestans exists as a metapopulation in central Mexico, and this population structure could be contributing to the repeated re-emergence of P. infestans in the United States and elsewhere.
authors.affiliation: Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Jianan
authors.identifier: http://orcid.org/0000-0002-7704-666X
authors.initials: J
authors.lastname: Wang
authors.affiliation: Laboratorio de Patología Vegetal, Universidad Michoacana de San Nicolás de Hidalgo, IIAF, Tarímbaro, Michoacán, 58880, México.
authors.forename: Sylvia P
authors.initials: SP
authors.lastname: Fernández-Pavía
authors.affiliation: Horticultural Crops Research Unit, USDA-ARS, Corvallis, OR, 97330, USA.
authors.forename: Meredith M
authors.initials: MM
authors.lastname: Larsen
authors.affiliation: Laboratorio de Patología Vegetal, Universidad Michoacana de San Nicolás de Hidalgo, IIAF, Tarímbaro, Michoacán, 58880, México.
authors.forename: Edith
authors.initials: E
authors.lastname: Garay-Serrano
authors.affiliation: Laboratorio de Patología Vegetal, Universidad Michoacana de San Nicolás de Hidalgo, IIAF, Tarímbaro, Michoacán, 58880, México.
authors.forename: Rosario
authors.initials: R
authors.lastname: Gregorio-Cipriano
authors.affiliation: Laboratorio de Patología Vegetal, Universidad Michoacana de San Nicolás de Hidalgo, IIAF, Tarímbaro, Michoacán, 58880, México.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Rodríguez-Alvarado
authors.affiliation: Horticultural Crops Research Unit, USDA-ARS, Corvallis, OR, 97330, USA.
authors.forename: Niklaus J
authors.identifier: http://orcid.org/0000-0003-1656-7602
authors.initials: NJ
authors.lastname: Grünwald
authors.affiliation: Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Erica M
authors.identifier: http://orcid.org/0000-0003-3512-2107
authors.initials: EM
authors.lastname: Goss
mesh_terms: D005828:Genetics, Population; D008800:Mexico; D055750:Phytophthora infestans / Q000235:genetics*; D010935:Plant Diseases / Q000382:microbiology*; D011198:Solanum tuberosum / Q000382:microbiology*
keywords: 
  Phytophthora infestans
  ; Oomycete; Toluca Valley; genetic variation; invasive pathogen; plant pathogen; population structure; potato