Variation among British isolates of potato leafroll virus

Abstract

SUMMARYTwenty isolates of potato leafroll virus (PLRV) were readily transmitted by Myzus persicae from a wide range of potato cultivars to Physalis floridana. The isolates also infected Montia perfoliata but not turnip or broad bean, and all were readily detected by direct enzyme‐linked immunosorbent assay. Four isolates, selected to represent the range of differences in severity of symptoms in P. floridana, also induced symptoms of differing severity in M. perfoliata, but their virulence in one species did not necessarily parallel that in the other. In general, virus concentration increased with increasing symptom severity. None of these four isolates was transmitted readily by Macrosiphum euphorbiae and their particles were antigenically indistinguishable in gel‐diffusion precipitin tests.Further tests on one PLRV‐infected potato plant from which virus was at first not transmitted by M. persicae showed that it contained a poorly‐transmissible isolate (isolate 15). The inefficient transmission of this isolate could not be attributed to inadequate uptake or retention by M. persicae of virus from P. floridana, and aphids failed to transmit isolate 15 when it was acquired from purified preparations in membrane‐feeding tests. Although the poor aphid transmissibility of isolate 15 is therefore an intrinsic property of its particles, these were antigenically indistinguishable from the particles of readily aphid‐transmissible isolates.Immunoelectron microscopy tests showed that PLRV and beet mild yellowing virus are antigenically closely related.