Biological and molecular characterization of Moroccan watermelon mosaic virus and a potyvirus isolate from Eastern Sudan

A potyvirus (Su-94-54) was isolated from a naturally infected snake cucumbe r (Cucumis melo var. flexuosus) plant with severe mosaic and leaf deformati on symptoms collected in Eastern Sudan. This isolate has a host range limit ed to cucurbits and is serologically distantly related to Moroccan watermel on mosaic virus (MWMV) and to Papaya ringspot virus (PRSV). Coat protein se quence analysis of Su-94-54 and MWMV and comparison with other potyviruses indicate that Su-94-54 is more closely related to MWMV than to any other po tyvirus. Based on the amino acid sequence identity in the core part of the coat protein with MWMV (86%), this isolate could be regarded as a distinct species. However, because of biological, cytological, and serological affin ities with MWMV, we propose that this isolate be considered as a strain of MWMV, possibly an evolutionary intermediate between MWMV and PRSV, until mo re is known on the structure of the PRSV subgroup within the genus Potyviru s.