DAS-ELISA quantification of resting spores of Olpidium virulentus in roots and correlation between resting spore density in soil and severity of lettuce big-vein disease

A method to quantify resting spores of Olpidium virulentus, fungal vector of Mirafiori lettuce big-vein virus, which causes lettuce big-vein disease, in lettuce roots was developed using a DAS-ELISA with a polyclonal antibody against the resting spores and used to evaluate the relationship between the resting spore density in soil and disease severity. When lettuce seedlings were grown on soils containing a powder made from diseased roots with a known number of resting spores, symptoms developed from ca. 10² spores/g of soil or more. This simple method can be used in soil diagnosis and risk assessment of the disease.