Tomato black-ring: a new virus disease

A new virus disease of tomatoes is described for which the name tomato black-ring is suggested. The host range of the virus is wide but no insect vector has yet been identified. The longevity in vitro of the virus is 7 days or longer, the thermal inactivation point is about 58° C. and the concentration of the virus in the host plant is low. Tomato black-ring is essentially a disease of young plants which rapidly lose their symptoms if they survive the severe initial infection. The virus is carried without symptoms by a large number of miscellaneous plants. Note added in proof. In a private communication Kassanis has pointed out that the tomato black ring virus produces enations on the undersides of the leaves of cucumber. The writer has confirmed this but finds that the enations develop only in the greenhouse type of cucumber, never on the outdoor or ridge variety. The enations do not seem to develop under winter conditions. The writer's best thanks are due to Miss Margaret Short for her assistance in this work and to Dr Roy Markham for taking the photographs.