Detection and partial characterization of a second closterovirus associated with little cherry disease, little cherry virus-2

Little cherry disease (LChD) is a complex and serious viral disease of cherry. Although originally described almost 70 years ago, there has been little progress in identifying the causal agent of the disease due to the difficulty in obtaining purified virus from infected trees. This problem was partially overcome in 1997 when the compete sequence of a closterovirus associated with LChD, Little cherry virus (LChV), was published. This virus could be associated with some, but not all, trees with LChD, indicating that another virus was also involved. We report here the partial characterization of a second closterovirus associated with LChD, Little cherry virus-2 (LChV-2), and in order to differentiate the two LChD-associated viruses, we refer to LChV as Little cherry virus-1 (LChV-1). LChV-2 is a new closterovirus with molecular similarities to Grapevine leafroll-associated virus-1 (GLRaV-1) and GLRaV-3 but only distantly related to LChV-1. Based on limited sequence comparisons, LChV-2 is the same virus previously identified in association with LChD in Canada. In reverse transcription-polymerase chain reaction detection assays using specific oligonucleotide primers to either LChV-1 or LChV-2, 27 of 28 isolates of LChD tested positive to one or both of these viruses originating from Europe and North America. These results would further confirm the association of LChV-2 with LChD. One isolate, however, tested negative to both LChV-1 and LChV-2, indicating that while this report brings us a step closer to understanding LChD, further work is required to confirm the causal agents of LChD.