Further characterization of lettuce chlorosis closterovirus
In the 1980s, in the Imperial Valley in California (US) yellowing symptoms were observed on weeds, lettuce, sugarbeet and the plants were found to be infected by lettuce infectious chlorosis closterovirus (EPPO A1 quarantine pest). In more recent years, stunted lettuces with yellow leaves and interveinal chlorosis were collected in 1992/1993 in the Imperial valley but lettuce infectious chlorosis closterovirus could not be detected. In fact authentic lettuce infectious chlorosis has not been detected in California in lettuce crops for the last 10 years. The symptoms seen in the 1990s are associated with a new distinct lettuce chlorosis closterovirus (LCV - see EPPO RS 97/018 and 98/085- EPPO Alert List). This virus was purified, partially characterized and polyclonal antisera were produced and used to study the disease in the field. Based on particle morphology and symptoms, LCV resembles other closteroviruses. The particle length is estimated at 750-950 nm. In general symptoms on lettuce of LCV and lettuce infectious chlorosis are indistinguishable. But Western blot analysis with the LCV antisera can distinguish the two viruses. In experimental lettuce plots, LCV was present during the 1995/1997 growing seasons. Yield losses were observed in symptomatic plants, and little yield loss in infected but asymptomatic plants. However it was difficult to conclude whether yield loss was due to the presence of the virus, as infected plants were also infested by Bemisia tabaci which causes feeding damage.
McLain, J.; Castle, S.; Holmes, G.; Creamer, R. (1998) Physicochemical characterization and field assessment of lettuce chlorosis virus.
Plant Disease, 82(11), 1248-1252.