Cucumber Necrosis Virus Is a Member of the Tombusvirus Group

Research Station, Agriculture Canada, 6660 NW Marine Drive, Vancouver, British Columbia, Canada V6T 1X2 The electrophoretic patterns of dsRNA species isolated from cucumber plants infected with cucumber necrosis virus (CNV) and from Nicotiana clevelandii plants infected with tomato bushy stunt virus (TBSV) were almost identical and differed greatly from the electrophoretic patterns of dsRNA species isolated from tobacco plants infected with tobacco necrosis virus (TNV). Hybridization with cloned cDNA of CNV showed that there was extensive homology between the nucleic acids of CNV and TBSV but not between those of CNV and TNV. Gel diffusion tests and ELISAs showed no serological relationship between CNV and five tombusviruses. TBSV-infected N. clevelandii plants showed some cross-protection against infection by CNV but not against infection by carnation ringspot virus. CNV therefore resembles TBSV more than TNV and should be classified as a tombusvirus. Keywords: cucumber necrosis virus, tombusvirus, taxonomy Received 7 September 1987; accepted 19 October 1987.