The role of alternative hosts of Polymyxa betae in transmission of beet necrotic yellow vein virus (BNYVV) in England

The host range of beet necrotic yellow vein virus (BNYVV) and Polymyxa betae was determined by growing plants in naturally infested soils from rhizomania outbreaks in England. Apart from Beta vulgaris, plant species infected by BNYVV were included in the families Chenopodiaceae (Atriplex patula, Chenopodium bonus-henricus, C. hybridum, C. polyspermum and Spinacia oleracea), Amaranthaceae (Amaranthus retroflexus) and Caryophyllaceae (Silene alba, S. vulgaris, S. noctiflora and Stellaria graminea). Only P. betae isolates from B. vulgaris, C. polyspermum and S. oleracea were found to be able to transmit BNYVV back to sugar beet. When a range of weed plants from infected fields were tested, none were found to be infected by BNYVV. Therefore, it seems likely that the weed hosts play only a minor role in the spread of rhizomania disease compared to that of sugar beet, other Beta vulgaris crop types or spinach.