Citrus tristeza virus (CTV) produces more than thirty 3'- or 5'-terminal subgenomic RNAs (sgRNAs) that accumulate to various extents during replication in protoplasts and plants. Among the most unusual species are two abundant populations of small 5'-terminal sgRNAs of approximately 800 nucleotides (nt) termed low-molecular-weight tristeza (LMT1 and LMT2) RNAs. Remarkably, CTV replicons with al...

During routine graft indexing of Rubus clones at the USDA-ARS Horticultural Crops Research Laboratory in Corvallis, Oregon, a ‘Glen Clova’ plant that originated in Scotland induced severe symptoms including stunting and apical necrosis when grafted on ‘Munger’ black raspberry (Rubus occidentalis). Cloning of viral dsRNA obtained from the plant and sequence analysis indicated the presence of a n...

Forty years ago, an unusual name— closterovirus—was coined for an unusual group of elongated plant viruses (BarJoseph and Hull, 1974). This essay reflects my personal encounter with these viruses between 1966 and 1986, a period that could be considered the beginning of the emergence of the Closteroviridae as an exciting complex virus family. The first two viruses assigned to this group, Beet ye...