Chenopodium necrosis: a distinctive strain of tobacco necrosis virus isolated from river water

A distinctive strain of tobacco necrosis virus (TNV) of unknown source was repeatedly isolated from water of the River Avon (Warwickshire) and two of its tributaries (R. Swift and R. Alne) using a technique developed for the concentration and isolation of water-borne bacteriophages. The same strain was isolated from the rivers Cam and Thames and from Lake Esthwaite (Cumbria) together with tomato bushy stunt virus. The TNV strain, designated Chenopodium necrosis (TNV-CN) was mechanically transmissible to C. amaranticolor and C. quinoa in both of which it caused local lesions and systemic infection. TNV-CN caused no infection when inoculated to tobacco (Nicotiana tabacum cv. White Burley) plants. The virus was not adsorbed to soil, could be isolated from leachate of soil in which systemically infected C. quinoa were grown and C. quinoa plants became infected when grown in soil watered with suspensions of the virus. The virus was not transmitted by Myzus persicae but was vectored by the zoospores of a lettuce isolate of Olpidium brassicae. TNV-CN was infective after 10 min at 85 °C., 3 wk at 20 °C and when diluted to 10^-8 but not 10^-9. Purified virus preparations contained c. 26 nm isometric virus particles. TNV-CN contained single-stranded RNA (mol. wt 1·5 × 10⁶) and one protein (mol. wt c. 26·4 × 10³) which co-electrophoresed in polyacrylamide gels with the protein of the D strain of TNV (TNV-D). Analytical centrifugation of TNV-CN indicated a single component virus with the same sedimentation coefficient (s₂₀, w= 115S) and buoyant density (1·385) in a CsCl gradient as those of TNV-D. TNV-CN and TNV-D were indistinguishable serologically.