Some Properties of a Phloem‐Limited Non Mechanically‐Transmissible Grapevine Virus

Abstract

Abstract Grapevine phloem‐limited isometric virus (GPLIV) is the name proposed for a non mechanically‐transmissible virus found in Italian and Tunisian grapevines. In density gradient centrifugation purified virus preparations sedimented as two components: T, made up of empty protein shells, and B, composed of intact nucleoprotein particles. B particles had a buoyant density of 1.45 g/cm 3 at equilibrium in CsCl and contained 35% RNA consisting of a single molecule with an apparent size of 7.4 kb. The coat protein consisted of a single species with a mol.wt of 28,000 daltons. Purified virus preparations did not infect herbaceous hosts by manual inoculation. A specific antiserum with a titre of 1: 64 raised in rabbits, was used for identification of, GPLIV in field‐grown Tunisian grapevines and in leafroll‐affected Italian vines before and after heat treatment. Although heat treatment eliminated the virus from the majority of the plants, leafroll symptoms persisted in several GPLIV‐free vines, indicating that there is no clear‐cut relationship between GPLIV and this disease.