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United States Department of Agriculture

Agricultural Research Service

Title: Selection for Fungicide Resistance Within a Growing Season in Field Populations of Phytophthora Infestans at the Center of Origin

Authors
item Grunwald, Niklaus
item Sturbaum, Anne - CEEM/PICTIPAPA
item Romero Montes, Gaspar - CEEM/PICTIPAPA
item Garay Serrano, Edith - CEEM/PITIPAPA
item Lozoya-Saldana, Hector - CEEM/PITIPAPA
item Fry, William - CORNELL UNIVERSITY

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 10, 2006
Publication Date: November 16, 2006
Citation: Grunwald, N.J., Sturbaum, A.K., Romero Montes, G., Garay Serrano, E., Lozoya-Saldana, H., Fry, W.E. 2006. Selection for fungicide resistance within a growing season in field populations of Phytophthora infestans at the center of origin. Phytopathology. 96(12):1397-1403.

Interpretive Summary: The central highlands of Mexico should provide an optimal testing ground for evaluating the potential threat of selection for resistance to fungicides in the population of Phytophthora infestans. P. infestans is known as the causal agent of potato late blight. We evaluated the hypotheses that exposure to several fungicides commonly used for control of potato late blight would lead to selection for fungicide resistance and a lower genotypic diversity of the population. We compared populations that had not been exposed to any fungicide with populations that had been exposed to several applications of each of the fungicides. This study provides novel baseline data and shows that the fungicides fluazinam, cymoxanil, dimethomorph, metalaxyl and propamocarb have a wide range of fungicide sensitivities. Directional selection towards resistance combined with a reduction in genetic diversity of the P. infestans population was only observed for the fungicide metalaxyl. The results obtained provide direct experimental support for continuing vigilance regarding further introductions of exotic strains of P. infestans into the US.

Technical Abstract: The central highlands of Mexico should provide an optimal testing ground for evaluating the potential threat of selection for resistance to fungicides in the population of Phytophthora infestans. We evaluated the hypotheses that exposure to the fungicides azoxystrobin, cymoxanil, dimethomorph, fluazinam, metalaxyl, and propamocarb hydrochloride would lead to (1) a shift in the sensitivity distributions, i.e. selection, and (2) a lower genotypic diversity of the population. We compared populations that had not been exposed to any fungicide with populations that had been exposed to several applications of each of the fungicides within a single field season. This study provides novel baseline data and shows that the fungicides fluazinam, cymoxanil, dimethomorph, metalaxyl and propamocarb have a wide range of fungicide sensitivities. Directional selection towards resistance combined with a reduction in genetic diversity of the P. infestans population was only observed for the fungicide metalaxyl. The results obtained provide direct experimental support for continuing vigilance regarding further introductions of exotic strains of P. infestans into the US.

Last Modified: 10/1/2014
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