ABSTRACT
The classification of viruses in the closterovirus group had its beginnings in Brandes and Welters' group 12. Clover yellows virus (CYV), described by Ohki and co-workers, is classified as a member of the closterovirus group by the ICTV. The virus particles measured 1700 × 12 nm in negatively stained leaf dip preparations and exhibited pronounced cross-banding with a 3.7-nm pitch. CYV is transmitted by Aphis craccivora, but the mode of transmission has not been reported. In thin-section studies, white clover phloem cells contained inclusions of aggregated particles, and associated with the particles were fibril-containing vesicles. CYV has been found in naturally infected crimson clover (Trifolium incarnatum) and white clover (T. repens) in Japan.
