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 fr om rhizomania outbreaks in England. Apart from Beta vulgaris, plant sp ecies infected by BNYVV were included in the families Chenopodiaceae ( Atriplex patula, Chenopodium bonus-henricus, C. hybridum, C. polysperm um and Spinacia oleracea), Amaranthaceae (Amaranthus retroflexus) and Caryophyllaceae (Silene alba, S. vulgar is, S. noctiflora and Stellari a graminea). Only P. betae isolates from B. vulgaris, C. polyspermum a nd S. oleracea were found to be able to transmit BNYVV back to sugar b eet. When a range of weed plants from infected fields were tested, non e 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 dise ase compared to that of sugar beet, other Beta vulgaris crop types or spinach.