High sequence variability among Little cherry virus Isolates occurring in British Columbia

The LC5 isolate of Little cherry virus (LChV-LC5) is one of at least two distinct viruses contributing to a severe disease of cherry (Little cherry disease [LChD]) in British Columbia. A near-complete nucleotide sequence of LChV-LC5 is available as well as polyclonal antibodies against LChV-LC5 coat protein produced in bacterial cells. A survey for LChV-LC5-infected trees in the Okanagan Valley and Kootenay region of British Columbia was carried out using enzyme-linked immunosorbent assays (ELISA) and LChV-LC5 antibodies. Reverse transcriptase polymerase chain reaction (RT-PCR) and sequence analysis of four different regions of the genomes of 31 of these isolates have been conducted. A high level of sequence variability was found: nucleotide sequence divergence between LChV-LC5 and the other sequenced isolates ranged from 0 to 19.7%, and amino acid sequence divergence ranged from 0 to 9.1%. Further examination of RT-PCR and sequence data identified six discrete groups of isolates, including a group identical to LChV-LC5. The high level of divergence in LChV-LC5 isolates occurring in British Columbia suggests that caution should be used in the selection of methods used for diagnosis during surveys for this virus.