Partial characterization of a closterovirus associated with apple mealybug-transmitted little cherry disease in North America

Little cherry disease (LChD) is a serious economic problem of sweet cherry production in western North America where apple mealybug is the principle vector. LChD is associated with a distinct species of double-stranded (ds) RNA. In this study, filamentous virus particles were purified from LChD-infected trees and shown to contain single-stranded RNA corresponding to the previously reported dsRNA isolated from infected trees. The virus particles were characterized and were similar to monopartite members of the genus Closterovirus. A portion of the genome was sequenced and found to be most closely related to the RNA-dependent RNA polymerase of Grapevine leafroll-associated virus-3, a mealybug-transmitted closterovirus. The characteristics of the mealybug-transmitted Little cherry virus in North America are very different from those of a closterovirus associated with a similar disease in Europe.