Abstract
The multiplication and distribution of tobacco mosaic virus in Nicotiana tabacum cv. Samsun NN leaves were investigated using the fluorescent antibody technique, in relation to the local lesion development. Virus antigen was first detected 24hr after inoculation in cell groups in the epidermal and palisade layers as well as in a few cells of spongy layer. Thereafter, progressive cell-to-cell spread of the antigen in leaf tissues was observed, and 32hr after inoculation, the stained areas were in the form of a cell group extending from the upper epidermal to the lower epidermal layer. By this time the virus antigen was also found in phloem cells, suggesting that virus long distance movement had begun. Necrosis was discovered in one or two cells of the upper spongy layer located in the central part of the stained areas 36hr after inoculation. Thereafter, cell necrosis spread rapidly in the spongy layer, and then in the palisade layer and upper and lower epidermis. When local lesions became visible 44hr after inoculation, necrosis had already spread throughout the greater part of the stained area. However, a few cells bordering the lesions contained the virus antigen and had no necrosis. Thereafter, continuous cells become progressively infected and necrosis developed into the inner cells, increasing the size of the local lesions. In N. tabacum cv. Samsun, the progressive spreading pattern of the virus antigen was similar to that of N. tabacum cv. Samsun NN until cell necrosis first appeared in the latter.
