Isolates of RBDV occurring in the field at East Malling Research Station (EMRS), and an isolate from raspberry seed imported from the USSR, differed from the Scottish type isolate (D200) in that they infected red raspberry cultivars that are resistant to, possibly immune from, D200. Of several red raspberry, blackberry and hybrid berry cultivars and EMRS raspberry selections graft-inoculated with these recently discovered RBDV isolates, only 2 raspberry cultivars (Haida and Rannaya Sladkaya) and 1 EMRS selection did not become infected. Differences in the conclusions reached in 2 previous studies on the inheritance of resistance to RBDV in raspberry can be explained by the use of virus isolates that differed in Rubus host range.