Abstract

Analysis by electrophoresis in polyacrylamide gels, followed by silver staining, of dsRNA extracted from many samples of raspberry leaves infected with raspberry leaf mottle virus and/or raspberry leaf spot virus failed to detect reliably any significant quantities of dsRNA species in excess of 1.0 x 10⁶ MW. This contrasts with results reported from Canada where 3 dsRNA species of estimated MW 2.6 x 10⁶, 1.6 x 10⁶ and 1.1 x 10⁶ were consistently associated with infection by RLSV but none were associated with RLMV. However, in Scotland, 4 dsRNA species of estimated MW 2.4 x 10⁶, 1.6 x 10⁶, 0.7 x 10⁶ and 0.3 x 10⁶ were detected in raspberry infected with apple mosaic virus. These results suggest that the dsRNA species reported from Canada are not those of RLSV but are probably those of a second virus, possibly an ilarvirus, which occurs together with RLSV and/or induces similar symptoms. A few samples from plants infected by RLMV and RLSV contained very small amounts of 2 dsRNA species of estimated MW 4.7 x 10⁶ and 4.5 x 10⁶. It is not known whether these species are those of RLMV and RLSV.