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United States Department of Agriculture

Agricultural Research Service


Location: Vegetable Crops Research

Title: Analysis of genetic and pathogenic variation among Alternaria solani in a potato production region

item Weber, Brooke
item Halterman, Dennis

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2012
Publication Date: 12/1/2012
Publication URL:
Citation: Weber, B., Halterman, D.A. 2012. Analysis of genetic and pathogenic variation among Alternaria solani in a potato production region. European Journal of Plant Pathology. 134(4):847-858.

Interpretive Summary: Many specimens of the potato early blight pathogen, Alternaria solani, were collected from a single location within a popular potato growing region of Wisconsin. Analysis of these specimens revealed an unexpected amount of differences within their genomes, which contrasts with the general thought that localized populations are relatively uniform. We also found that different specimens can have a different effect on potato, with some causing more disease than others. These results are important because there was little or no previous data available regarding the makeup of A. solani populations within a single field. Results of this analysis has impacted the way that we perform resistance evaluations in the lab or greenhouse since single pathogen strains, which may not be indicative of field conditions, should no longer be used.

Technical Abstract: A two-year survey was conducted in a potato production region to investigate the genetic variability within naturally infecting populations of Alternaria solani, the cause of early blight in potato, and between species A. solani and A. dauci. Genetic diversity among 151 isolates was assessed using seven random amplified polymorphic DNA (RAPD) markers and sequence analyses of portions of the internal transcriber spacer (ITS) region and Alt a1 gene. Isolates were grouped according to the presence or absence of polymorphic bands into 19 assigned genotype categories to examine the distribution patterns of genetically distinct isolates within and between years. Seven genotype categories were found spanning both years with categories 6 and 13 being the most prevalent. Five unique genotypes were found only in 2008 and seven were found only in 2009. No variation was observed among isolates of A. solani based on the sequence analysis, but a distinction between A. solani and A. dauci was identified. Pathogenicity was also assessed using a tissue culture plantlet assay on four isolates and two reference cultures to determine if variation existed. A significant virulence effect was observed among isolates.

Last Modified: 10/18/2017
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