Characterization of Solanum dulcamara yellow fleck-ob: a tobamovirus that overcomes the N resistance gene

A tobamo-like virus, Solanum dulcamara yellow fleck-Ob (SDYFV-Ob), originally isolated from green pepper (Capsicum annuum L.), possessing morphological and capsid protein properties characteristic of tobamoviruses, spread systemically in inoculated Nicotiana tabacum L. 'Xanthi nc' (NN) and Nicotiana glutinosa L., both of which contain the N gene for resistance to tobacco mosaic virus. The virus, previously considered a strain of tomato mosaic virus (ToMV), showed strong homology in dot blot hybridization with Solanum dulcamara yellow fleck tobamovirus (SDYFV), but not to several others, including ToMV. SDYFV and SDYFV-Ob induced similar symptoms in a variety of hosts; however, SDYFV did not spread systemically in hosts containing the N resistance gene. The level of accumulation of SDYFV-Ob in tobacco protoplasts was comparable to that of another tobamovirus (ToMV-LS1). In N. tabacum 'Xanthi nc' (NN), SDYFV-Ob did not complement systemic movement of other tobamoviruses, Furthermore, in 40% of the plants, systemic spread of SDYFV-Ob was prevented by coinoculation with other tobamoviruses. These results are discussed in relation to possible resistance mechanisms