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Natural Occurrence of Phytophthora infestans Causing Late Blight on Woody Nightshade (Solanum dulcamara) in New York

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The oomycete, Phytophthora infestans, is a devastating pathogen of potato worldwide. Several strains of P.infestans are able to infect other cultivated and weed species of the family Solanaceae and cause symptoms similar to late blight on these hosts. Changes in P. infestans populations have stimulated investigations to determine if tomato/potato strains from more recent immigrant populations infect a wider host-range than those from the older population. Expansion of the host range may be one of the mechanisms involved in pathogenic changes in natural populations of P. infestans and to determine its significance, it is necessary to establish if the pathogen strains on non-potato hosts represent distinct genotypes/populations or are freely exchanging with those on tomato or potato. This paper reports characterization of P. infestans isolates from a Solanaceous host growing within and around fields of blighted potatoes and tomatoes in New York and the comparison with isolates collected from adjacent infected hosts. Isolates were characterized for mitochondrial DNA (mtDNA) haplotype, mating type, metalaxyl resistance, allozymes of glucose-6-phosphate isomerase and peptidase, and DNA fingerprint with the RG57 probe. Analysis showed close similarity of the woody nightshade isolates to potato and tomatoes isolates. Moreover, tomato and potato strains had distinctly similar fingerprints. Potato growers should be aware that both weed and cultivated Solanaceous species can be infected with P. infestans and may serve as clandestine reservoirs of inoculum. Because some of these plants do not show conspicuous symptoms, they may escape detection and fail to be either removed or treated and so may play a major role in the introduction and spread of pathogens to new locations.
K. L. Deahl , F. Perez , C. J. Baker , R. W . Jones , L. Cooke , M. McGrath
USDA Scientist Submission
Plant disease 2010 8 v.94 no.8
Journal Articles, USDA Authors, Peer-Reviewed
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