Submitted to: Fitopatologia
Publication Type: Proceedings
Publication Acceptance Date: February 27, 1998
Publication Date: N/A
Technical Abstract: Three types of evidence relating to the center of origin of Phytophthora infestans - historical, biological, and genetic - were evaluated with the specific goal of addressing the hypothesis that this pathogen evolved in South America. Claims of historical evidence indicating the presence of late blight in South America before the 1840s were found to be groundless. Most of the historical descriptions were too vague to be able to associate them with any specific disease. Biological evidence consisted of resistance genes in wild Mexican Solanum species (and their absence elsewhere), high virulence diversity of the fungus in Mexico, and the discovery of the A2 mating type in Mexico. There were four lines of genetic evidence: i) the closest relative of P. infestans, P. mirabilis, is also endemic to Mexico; ii) the highest diversity for molecular markers occurs in Mexico; iii) populations in all other countries until very recently contained only a single clonal lineage of the pathogen; and iv) there was genetic subdivision among populations in Mexico. All three types of evidence clearly point to Mexico as the center of origin for P. infestans, and are sufficient to falsify the hypothesis of a South American origin.