A new virus isolated from Ranunculus hyb. with particles resembling supercoiled filamentous nucleocapsids

An apparently new virus (coded Rn3), was isolated from a plant of Ranunculus hyb. (cv. Grazia) collected in Liguria, northern Italy, which showed mosaic and distortion. The virus was transmitted to test plants by sap inoculation. Both crude sap and purified preparations from infected Nicotiana benthamicma, and N. clevelandii contained filaments about 3 nm wide, in certain conditions assuming a duplex form about 9 nm wide, sometimes pseudobranched. Purified virus was used to obtain an antiserum. A major protein of about 43 kDa was specifically detected in Western blots from purified preparations and total protein extracts of infected leaves. Serological cross reactions with viruses of similar morphology were tested by Western blotting; preparations of rice stripe tenuivirus (RSV), citrus ringspot virus (CtRSV) and Rn3 were challenged with polyclonal antisera against RSV, maize stripe tenuivirus, rice hoja blanca tenuivirus, CtRSV, tulip mild mottle mosaic virus and Rn3. No heterologous reactions with Rn3 were detected. Electrophoresis of dsRNA extracted from infected N. benthamiana leaf tissue under non-denaturing conditions in 5% PAGE gave two specific bands of about 1.5 and 1.8 Kbp. DAS ELISA was used to index the distribution of the virus in the field; preliminary results showed a 2.5% incidence of Rn3 infection in 316 ranunculus plants sampled in two different areas in Liguria.