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Ann. Tabac, 1995, sect. 2-27, p. 7-16., ISSN.0399-0345

Taxonomic relationships between the distinct populations of potato virus Y based on the biological, serological and genomic properties. Definition of pathotypes on potato

LE ROMANCER M.
INRA, Station de Pathologie Végétale, Rennes-le-Rheu, France.
Three independent taxonomic keys connected with the host specificity are currently used to describe the biological variability within the potato virus Y (PVY) species that infects tobacco, tomato, pepper and potato. Differences in the taxonomic criteria employed do not permit comparative studies between the different viral populations, which nevertheless share several common biological, serological and genomic properties. Of the three classifications, that of the pepper strains of PVY, based on the pathotype-genotype relationships, offers the best characteristics, while that of potato strains appears to be perfectible. Using several virus-specific or strain group-specific resistance genes in the Solanum genus, it is possible to transpose the pathotype-genotype approach to classify the potato strains. Based on the response of a limited range of potato genotypes, four pathotypes of PVY can be defined. The first three pathotypes, designated 1, 2 and 1-2 match the classical YC, YO and YN strain groups respectively, while the fourth one (1-2-3) corresponds to the new YNTN strains. This taxonomic approach highlights the genetic basis underlaying the original classification and clearly indicates that it is specific to the potato strains only. However, the selectivity of this method of classification appears to be the main drawback because it artificially strengthens the idea of the existence of several distinct populations of virions or sub-species of PVY, even if the point remains controversial in the literature. To overcome this obstacle, we propose to pool all the potato, tobacco, tomato and pepper strains in a common classification combining some genomic and serological criteria to the biological ones, where the former enable the definition of the species and its main subdivisions, and the latter acutely indicate the intraspecific variability within the PVY taxon.