Serological and molecular variability of watermelon mosaic virus (genus Potyvirus).

Watermelon mosaic virus (WMV, genus Potyvirus) is very common in cucurbits worldwide, but its variability has been little studied. In France, where WMV has been known since 1974, unusually severe symptoms on zucchini squash have been found to be associated with WMV since 1999. We have developed serological and molecular tools to study WMV variability and the origin of severe strains. Eight monoclonal antibodies were obtained, characterized by epitope mapping, and used to assess the serological variability of 42 isolates from different countries. Sequence analysis based on the NIb-CP region revealed an important variability, with three distinct molecular groups. These analyses also suggested frequent intraspecific recombination in WMV.