Clones of cauliflower mosaic virus identified by molecular hybridization in turnip leaves.

Mechanical inoculation of turnip leaves with cauliflower mosaic virus (CaMV) results after one to two weeks in the appearance on these leaves of local lesions. Local lesions were detected by hybridization of radioactive CaMV DNA with nucleic acid immobilized in leaf skeletons by solvent extraction, proteinase digestion, and alkali treatment. The pattern of lesions detected as dark circles on autoradiographs of the washed leaf skeletons was the same as that detected by staining of solvent-extracted leaves for starch. Starch lesions appeared as white areas against a dark purple back-ground. These lesions were first detected between 5 and 8 days after inoculation and grew in size until 10 days after inoculation. Lesions were also detected by staining solvent-extracted and proteinase digested leaves with ethidium bromide. The lesions appeared as dark areas in a bright fluorescent background, and were found in the same positions as the starch lesions.