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Genetic Structure of the Population of Pepino mosaic virus Infecting Tomato Crops in Spain

First, fourth, and seventh authors: Departamento de Biotecnología, E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, 28040 Madrid, Spain; second, third, and sixth authors: Departamento de Ecosistemas Agroforestales, Patología Vegetal, Universidad Politécnica de Valencia, Camino de Vera 14, 46022 Valencia, Spain; and fifth author: Departamento de Biotecnología, Instituto Nacional de Investigación Agraria y Alimentaria, 28040 Madrid, Spain

The population structure of Pepino mosaic virus (PepMV), which has caused severe epidemics in tomato in Spain since 2000, was analyzed. Isolates were characterized by the nucleotide sequence of the triple gene block and coat protein gene and, for a subset of isolates, a part of the RNA-dependent RNA polymerase gene. The full-length sequence of the genomic RNA of a Solanum muricatum isolate from Peru also was determined. In spite of high symptom diversity, the Spanish population of PepMV mostly comprised highly similar isolates belonging to the strain reported in Europe (European tomato strain), which has been the most prevalent genotype in Spain. The Spanish PepMV population was not structured spatially or temporally. Also, isolates highly similar to those from nontomato hosts from Peru (Peruvian strain) or to isolate US2 from the United States (US2 strain) were detected at lower frequency relative to the European strain. These two strains were detected in peninsular Spain only in 2004, but the Peruvian strain has been detected in the Canary Islands since 2000. These results suggest that PepMV was introduced into Spain more than once. Isolates from the Peruvian and US2 strains always were found in mixed infections with the European tomato strain, and interstrain recombinants were detected. The presence of different strains of the virus, and of recombinant isolates, should be considered for the development of control strategies based on genetic resistance.