Studies on infection and multiplication of plant viruses in variegated tobacco plants 2. infection and multiplication of tobacco mosaic virus in variegated leaves of tobacco nicotiana tabacum cultivar samsun nc

Nagao, N.

Science Bulletin of the Faculty of Agriculture Kyushu University 35(3-4): 129-136


Accession: 006508495

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The sensitivity of white (W) and green (G) areas of variegated tobacco leaves (N. tabacum cv. Samsun Nc) to infection and multiplication of tobacco mosaic virus (TMV) was compared. The number of local lesions produced on W was double that on G. The enlargement of local lesions was relatively faster on W; TMV concentration at 3-4 days after inoculation was 2-6 times higher in the lesions produced on G as compared to that in the lesions on W. The central and marginal tissues of local lesions developed on W and G were observed by EM to clarify the processes of collapse and necrotization of cells in relation to TMV multiplication. In the central tissues of lesions on both areas of W and G, all cells were completely collapsed, shrunken and star-shaped. In these cells, TMV particles were aggregated in crystalline form in altered electron-dense cytoplasm. The size and number of the virus-aggregates in G cells were greater than those in W cells. In marginal tissues of the lesions, various stages of cell necrotization were observed. The 1st events of cell necrotization were plasmolysis and rupturing of the tonoplast. Following these events, the plastids or chloroplasts burst and the continuity of the cytoplasmic membrane was lost. In W tissues, the loss of continuity in the cytoplasmic membrane occurred earlier than bursting of plastids. TMV particles were scattered in the cytoplasm with bursting of the tonoplast in W and G cells. No marked difference was observed in the ultrastructure of margins of the lesions from W and G. TMV particles were observed in the cytoplasm of several cells beyond the necrotic region. The fact that TMV concentration in local lesions on W is lower than that in the lesions on G, contrasting to higher sensitivity (in terms of lesion formation) of the former than the latter, may be attributed to the rapid cell necrotization in W cells as compared to that in G cells resulting in early inhibition of virus multiplication.