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Population Genetic Structure of Phytophthora infestans in Ecuador

April 1997 , Volume 87 , Number  4
Pages  375 - 380

Gregory A. Forbes , Ximena C. Escobar , Catalina C. Ayala , Jorge Revelo , Maria E. Ordoñez , Barbara A. Fry , Katharine Doucett , and William E. Fry

First and fifth authors: International Potato Center (CIP), P.O. Box 17-21-1977, Quito, Ecuador; second, third, and fourth authors: Instituto Nacional de Investigacion Agropecuaria (INIAP), Box 340, Quito, Ecuador; and sixth, seventh, and eighth authors: Department of Plant Pathology, 334 Plant Science, Cornell University, Ithaca, NY 14853

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Accepted for publication 19 December 1996.

The population genetic structure of Phytophthora infestans in Ecuador was assessed from 101 isolates collected from 1990 to 1992 and 111 isolates collected in 1993. All isolates were analyzed for mating type and allozyme genotype. Both samples were dominated (>95%) by a clonal lineage (EC-1) defined from neutral markers: 90/100 genotype for glucose-6-phosphate isomerase, 96/100 genotype for peptidase, A1 mating type, and a previously unreported nuclear DNA fingerprint. The remaining isolates belonged to the US-1 clonal lineage, which has a worldwide distribution. Isolates in the 1993 sample were analyzed for virulence and metalaxyl sensitivity. All representatives of EC-1 had complex patho-types, with three pathotypes representing >60% of the collection. There was variation for metalaxyl sensitivity. There was no evidence for geographical substructuring on the basis of neutral markers, but there was evidence for limited substructuring based on metalaxyl sensitivity and specific virulence. We hypothesize that EC-1 has been recently introduced to Ecuador.

© 1997 The American Phytopathological Society