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A study of luteoviruses involved in potato leafroll disease Ellis, Peter John

Abstract

In total, 801 samples of potato leafroll disease were collected and tested for potato leafroll virus (PLRV) and beet western yellows virus (BWYV) in 1986, 1987, and 1988 using triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) and virus-specific monoclonal antibodies. The samples represented 32 cultivars and originated in eight Canadian provinces and 12 American states. None of the samples tested positive for BWYV, whereas 772 (96.4%) tested positive for PLRV. Neither PLRV nor BWYV could be recovered, with aphid transfers to indicator hosts, from 28 of the 29 samples that tested negative for both viruses. PLRV was recovered from one sample that originally tested negative by TAS-ELISA; the indicator plant tested positive for PLRV by TAS-ELISA. Nucleic acid spot hybridization (NASH) using random primed and cloned cDNA probes was compared with double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and TAS-ELISA, and aphid transmission tests for detection and identification of PLRV and BWYV in 165 potato leafroll disease samples. All of the samples tested negative for BWYV with each of the assay procedures. PLRV was detected in all of the samples with TAS-ELISA, NASH with a cloned cDNA probe for PLRV, and with aphid transmission to ground cherry (Physalis pubescens). Both DAS-ELISA and NASH using random primed cDNA produced one false-negative result. Shepherd's purse (Capsella bursa-pastoris) was a host for 72% (119/165) of the PLRV isolates. The susceptibility of potato to BWYV was tested by inoculating Russet Burbank with three isolates of BWYV from Canada and four from the United States. Two of the isolates were in a mixed infection with PLRV. None of the isolates were transmitted by Myzus persicae to virus-free potato plants, either by themselves or in association with PLRV. Common weeds were surveyed in the potato-producing areas of British Columbia for PLRV and BWYV. In total, 10,098 weed samples, representing 98 species in 22 plant families, were collected and tested by TAS-ELISA from 1986 to 1989. BWYV was detected in 1% of the samples; the hosts were: chickweed, common groundsel, heart-podded hoary cress, hedge mustard, little western bittercress, prickly lettuce, shepherd's purse, and wild radish. PLRV was detected in three volunteer potato plants, two samples of shepherd's purse, and one black nightshade plant. The low incidence of PLRV in plants other than potato indicates that weeds are of minor importance in the epidemiology of potato leafroll disease in British Columbia.

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