A GLOBAL MARKER DATABASE FOR PHYTOPHTHORA-INFESTANS

A marker database was compiled for isolates of the potato and tomato l ate blight pathogen, Phytophthora infestans, originating from 41 locat ions which include 31 countries plus 10 regions within Mexico. Present ly, the database contains information on 1,776 isolates for one or mor e of the following markers: restriction fragment length polymorphism ( RFLP) ''fingerprint'' consisting of 23 bands; mating type; dilocus all ozyme genotype; mitochondrial DNA haplotype; sensitivity to the fungic ide metalaxyl; and virulence. In the database, 305 entries have unique RFLP fingerprints and 258 entries have unique multilocus genotypes ba sed on RFLP fingerprint, dilocus allozyme genotype, and mating type. A nomenclature is described for naming multilocus genotypes based on th e International Organization for Standardization (ISO) two-letter coun try code and a unique number, Forty-two previously published multilocu s genotypes are represented in the database with references to publica tions. As a result of compilation of the database, seven new genotypes were identified and named. Cluster analysis of genotypes from clonall y propagated populations worldwide generally confirmed a previously pu blished classification of ''old'' and ''new'' genotypes. Genotypes fro m geographically distant countries were frequently clustered, and seve ral old and new genotypes were found in two or more distant countries. The cluster analysis also demonstrated that A2 genotypes from Argenti na differed from all others. The database is available via the Interne t, and thus can serve as a resource for Phytophthora workers worldwide .