High similarity between tomato isolates of Pepino mosaic virus suggests a common origin

The almost simultaneous outbreaks of Pepino mosaic virus in tomato crops in different European and non-European countries, was reason to have a closer look at the relationship between these isolates and the original isolate from pepino. Fifteen isolates from tomato from different locations and the original pepino isolate, were compared on the basis of their symptomatology on a series of plant species. In addition, PCR fragments derived from the viral polymerase gene were sequenced and aligned. Both studies showed that the isolates from tomato clearly differed from the pepino isolate. The different tomato isolates, however, exhibited only minor differences to each other, both in symptomatology and nucleotide sequence. These results support the conclusion that the tomato isolates should be considered as a distinct strain (Mumford and Metcalfe (2001) Archives of Virology 146: 2455-2460; Van der Vlugt et al. (2000) Plant Disease 84: 103; Van der Vlugt et al. (2002) Bulletin OEPP/EPPO Bulletin 32: 503-508). Moreover, the high similarity of the different tomato isolates suggests the existence of a common source of infection for the recent outbreaks.