BEET WESTERN YELLOWS VIRUS IS NOT AN IMPORTANT COMPONENT OF POTATO LEAFROLL DISEASE IN CANADA AND THE UNITED-STATES

We tested 801 samples of potato leaves with leafroll-like symptoms for potato leafroll virus (PLRV) and beet western yellows virus (BWYV) us ing virus-specific monoclonal antibodies in triple-antibody sandwich e nzyme-linked immunosorbent assay (TAS ELISA). The samples represented 32 cultivars and originated in eight Canadian provinces and 12 states in the United States. None of the samples tested positive for BWYV, wh ereas 774 (96.6%) tested positive for PLRV. Neither virus could be rec overed via aphid (Myzus persicae) transfers to indicator hosts from 18 samples that tested negative for both viruses. Tubers collected from 134 of the samples were sprouted and retested by both TAS ELISA and a polyclonal antiserum-based double-antibody sandwich (DAS) ELISA. These tests confirmed the initial results. Absorbance readings, when differ ent, were consistently higher in TAS ELISA than in DAS ELISA. Aphid tr ansmission attempts confirmed the ELISA results. In other aphid transm ission trials, we were unable to transmit any of seven isolates of BWY V from infected groundcherry (Physalis pubescens) to potato, which ind icated that potato is not a host of BWYV.