Abstract

Lettuce big-vein disease causes leaf distortion and ruffling in affected lettuce plants.

This disease was first associated in 1983 with a rod-shaped virus named lettuce big-vein associated virus (LBVaV), which is transmitted by the obligately parasitic soil-inhabiting fungus, "Olpidium brassicae". However, in 2000, a second virus, "Mirafiori lettuce virus", was found in lettuce showing big-vein symptoms. Furthermore, since the lettuce infected with this virus alone developed big-vein symptoms, it is considered to be a main agent of the big-vein disease.