Cucumber mosaic virus associated RNA 5: causal agent for tomato necrosis.

A small replicating RNA, encapsidated with and dependent on, but not part of the viral genome, modifies disease expression depending on the host. In tomato plants, it causes a lethal necrotic disease which is probably the same as that which, in 1972, destroyed most of the field tomato crop in large regions of the French Alsace.