Cherry leaf roll virus causing a disease of Betula spp. in the United Kingdom

Abstract

A virus, serologically related to isolates of cherry leaf roll virus (CLRV) from Prunus avium (L.) L. and Sambucus nigra L. was transmitted to a range of herbaceous plants from leaves or roots of thirty-one of forty-seven trees of Betula spp . growing at two heathland sites in Berkshire. Ageing leaves of virus-infected individuals which had mild chiorotic blotches or ring and line patterns in July showed bright yellow ring and line patterns in October. In the season after B. verrucosa seedlings were inoculated with CLRV isolates, leaves developed chlorotic ring and blotch patterns; the symptoms being similar whether the inocula were originally isolated from S. nigra, P. avium or B. verrucosa . Palisade and mesophyll cells of naturally infected leaves of B. verrucosa contained chloroplasts in which granal organization was appreciably less distinct than that of chloroplasts from virus-free leaves. In many instances, virus-infected leaf cells had spherical virus-like particles about 30 mn in diameter contained within tubular structures in cell wall projections; these structures were not seen in virus-free material. An isolate of CLRV from B. verrucosa , purified from systemically infected leaves of Nicotiana clevelandii Gray by ammonium sulphate precipitation and differential centrifugation, contained two major components having sedimentation coefficients of 118s and 130s. Each component was composed of spherical particles with diameters in the range 26–30 nm and having buoyant densities in caesium chloride of 1·460 and 1·493 gm/cm ³ . Polyacrylamide gel electrophoresis of preparations from both buoyant components indicated that they each contained a single species of protein whose molecular weight was in the range 53,000–54,000 daltons.