Abstract
In a field where lettuce big-vein disease had occurred, the relationship between symptom expression and two viruses associated with the disease (Lettuce big-vein virus and Mirafiori lettuce virus) was investigated in a total of 60 lettuce cultivars (Lactuca saliva L.). Both viruses were detected in all lettuce cultivars. In the crisphead type, the degree of resistance to symptom expression was related to the stage at which the virus was detected, especially with Mirafiori lettuce virus. In the butterhead, cos, stem and red leaf types, both viruses were detected in the early growing stages, while few or no typical symptoms were observed at harvest.
