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United States Department of Agriculture

Agricultural Research Service

Title: A Global Marker Database for Phytophthora Infestans

Authors
item Forbes, Gregory - INTERNATIONAL POTATO CTR
item Goodwin, Stephen
item Drenth, Andre - UNIVERSITY OF QUEENSLAND
item Oyarzun, Pedro - INTERNATIONAL POTATO CTR
item Ordeniz, Maria - INTERNATIONAL POTATO CTR
item Fry, William - CORNELL UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 9, 1998
Publication Date: N/A

Interpretive Summary: Late blight, caused by the fungus-like Oomycete Phytophthora infestans, is one of the most serious constraints to potato and tomato production worldwide. The disease was effectively managed for decades in developed countries by frequent application of fungicides. However, recent migrations of highly destructive, fungicide-resistant strains have led to a aglobal resurgence of the disease, often with devastating consequences. Th cost of this disease to United States potato and tomato growers was estimated at over $200 million in 1994 alone; similar losses have occurred every year since 1992. In response, interest in the disease and its causal organism has increased dramatically, leading to a proliferation of new data. Unfortunately, lack of organization and standardization have limited the usefulness of these data. The purpose of this contribution was to collate information from 13 different studies into a coherent, organized, global database for P. infestans. Standardized methods for collecting and organizing data from 33 different countries were proposed. A standard nomenclature for strain identification was established to facilitate global communication. A limited analysis of the database revealed that isolates of P. infestans from Argentina were different from those in other South American countries, indicating a need for increased study. The database will be made available over the Internet. Use of a standard format for data collection, analysis, and storage will promote communication, facilitate collaboration, and thereby increase the utility of the data. This database will provide a needed resource to plant pathologists, other scientists, and potato and tomato growers worldwide in their attempts to devise improved methods for combating this globally devastating disease.

Technical Abstract: A marker database was compiled for isolates of the potato and tomato late blight pathogen, Phytophthora infestans, coming from 41 "sites": 31 countries and 10 regions within Mexico. Presently the database contains information on 1776 isolates for one or more of the following markers: RFLP "fingerprint" consisting of 23 bands; mating type; dilocus allozyme genotype; mitochondrial DNA haplotype; sensitivity to the fungicide metalaxyl; and virulence. Three hundred and five entries have unique RFLP genotypes and 258 entries have unique multilocus genotypes, composed of RFLP fingerprint, dilocus allozyme genotype and mating type. A nomenclature is described for naming multilocus genotypes based on the International Organization for Standardization (ISO) two-letter country code and a unique number. Forty-two previously published multilocus genotypes are represented in the database with reference to publications. As a result of compilation of the database, seven new genotypes were identified and named. Cluster analysis of genotypes from clonally propagated populations worldwide generally confirmed a previously published classification of "old" and "new" genotypes. Genotypes from geographically distant countries were frequently clustered, and several old and new genotypes were found in two or more distant countries. The cluster analysis also demonstrated that A2 genotypes from Argentina differed from all others. The database is available via Internet, and thus can serve as a resource for Phytophthora workers worldwide.

Last Modified: 12/21/2014
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