Flexuous filamentous particles of wineberry latent potexvirus (WLV) measured 620 ? 12 nm. Analysis of dsRNA from infected plants detected a major species of c. 5.7 ? 106 mol. wt and minor species of lower mol. wt. Purified virus particles formed a major and a minor buoyant density component in solutions of caesium salts with densities of 1.26 and 1.25 g/cm? in Cs2SO4 and 1.30 and 1.29 g/cm? in CsCl. The particles contained a single nucleic acid species, presumably single stranded RNA, and a single polypeptide of estimated mol. wt 2.78 ? 106 and 31 000 respectively. In indirect ELISA, purified particles of WLV and particles in plant sap failed to react specifically with antiserum to 9 carlaviruses, 12 potexviruses, 3 capilloviruses or apple chlorotic leafspot closterovirus, nor was WLV found to react with several of these antisera in immunosorbent EM or immunoblots. In Marion and Olallie blackberry, WLV in mixture with raspberry bushy dwarf virus (RBDV), but not RBDV alone, induced veinal line-pattern symptoms resembling those of calico disease reported from the USA.