STUDIES ON THE HOST RANGE, PROPERTIES AND MODE OF TRANSMISSION OF BEET RINGSPOT VIRUS

An apparently undescribed mechanically transmissible virus has been named beet ringspot virus (BRV). It occurs naturally in Scotland in sugar-beet, turnip, swede, potato and many kinds of weed plants. BRV is readily distinguished from raspberry ringspot virus by the symptoms produced in Chenopodium amaranticolor, French bean, tobacco and Petunia hybrida plants. BRV lost infectivity when heated for 10 min. at 63 degrees C. but not at 60 degrees C. : at 20 degrees C. its longevity in Vitro was about 3 weeks. BRV was precipitated by ammonium sulphate, ethanol and acetone. Protection experiments with tobacco plants, and serological tests, gave no evidence that BRV was related to tobacco ringspot, raspberry ringspot, potato bouquet or tobacco rattle viruses, but showed that viruses isolated from different host plants and from different localities were strains of BRV. BRV is soil-borne : in glasshouse experiments sugar-beet, beetroot, potato, turnip, swede, French bean, Fragaria vesca, oat and wheat plants often became systemically infected when grown in soil from the site of a disease outbreak, but the virus was restricted to the roots of many infected plants. When sugar-beet seedlings were grown in virus-containing soil, BRV was first detected in their roots, where its concentration increased, before progressively increasing amounts of virus were found in the shoots. Soils from five localities were found to contain BRV. BRV has been found only where the soil is light in texture, and often in fields where raspberry ringspot virus occurs.