An apparently undescribed virus, provisionally named raspberry yellow dwarf virus (RYDV), was isolated from naturally infected raspberry, strawberry, blackberry and several weed species by mechanical inoculation of sap to Chenopodium amaranticolor. The severe disease it caused in Malling Exploit raspberry usually occurred patchily in otherwise normal plantations: these patches increased in size from year to year. RYDV was differentiated from raspberry ringspot and tomato black ring viruses by the symptoms produced in C. amaranticolor, tobacco and Petunia hybrida. RYDV lost infectivity when sap was heated for 10 min at 61 C, diluted 10-5 or kept for 15 days at 18 C. RYDV was precipitated without inactivation by acetone and by ammonium sulphate.
Isolates of RYDV from different plants and localities, and of different virulence, were identified by plant-protection and serological tests. Such tests gave no evidence that RYDV was related to raspberry ringspot, tobacco ringspot, tomato black ring or cucumber mosaic viruses.
Raspberry and sugar-beet plants became systemically infected with RYDV when grown under glass in soil from a field where the disease had occurred in raspberry plants, and where the virus persisted in the soil for 3 years after the raspberry plants were removed. RYDV seems to be widely disseminated in England but recently introduced and rare in eastern Scotland.
Like raspberry ringspot and tomato black ring viruses, RYDV causes symptoms of the ringspot type in tobacco, has a wide natural and experimental host range, is soil-borne and of local importance. Such features seem characteristic of ringspot viruses as a group.