THE HOST-RANGE OF BEET YELLOWING VIRUSES AMONG COMMON ARABLE WEED SPECIES

Twenty common arable weed species were inoculated using Myzus persicae to transmit beet yellows virus (BYV), beet mild yellowing virus (BMYV ), and an isolate of beet western yellows viruses (BWYV) that did not infect beet. The viruses were detected by enzyme-linked immunosorbent assay (ELISA), in which monoclonal antibodies distinguished between BM YV and BWYV, and by aphid transmissions to indicator host plants. Sper gula arvensis, Stellaria media, Lamium purpureum and Papaver rhoeas we re susceptible to all three viruses whereas Senecio vulgaris, Capsella bursa-pastoris, Anagallis arvensis and Chrysanthemum segetum were sus ceptible to both BMYV and BWYV, and Matricaria perforata, Raphanus rap hanistrum, Veronica persica, Urtica urens and Viola arvensis were susc eptible to BWYV only. Atriplex patula, Chenopodium album and Portulaca oleracea were susceptible to BW only. Myosotis arvensis, Silene alba, Poa annua and Solanum nigrum were not susceptible to any of the virus es. Portulaca oleracea was shown for the first time to be a host of BW , and C. segetum a host of BMYV and BWYV. In spring 1991, 8% of weeds sampled in a field of autumn-sown oilseed rape contained BWYV. Tests o n weeds collected from an area of 'set-side' adjacent to sugar beet sh owed that 3% contained BMYV and 3% BWYV. No sampled weeds were infecte d with BYV. The role of weeds in the epidemiology of sugar beet virus yellows is discussed.