Abstract
Multiplication and distribution of cucumber mosaic virus during the development of systemic infection in tobacco plants (Nicotiana tabacum cv. Xanthi) inoculated to the middle leaf were investigated by the use of fluorescent antibody technique. After the virus multiplied in the inoculated leaf, the virus antigen was first detected in the upper stem and leaves, and later in the lower stem and roots. In the early stage of a long distance movement of the virus, the virus antigen was first observed in separate areas along the phloem. This mode of virus movement differed from that in the parenchyma tissue, in which the virus moved from cell to cell, suggesting that the virus move a long distance through sieve tubes. Thereafter the virus progressively spread from the infection site in the phloem to surrounding tissues and caused the systemic infection. In the upper leaves, the appearance of symptoms such as veinclearing and yellowing followed the distribution of virus antigen in the tissues. After the virus antigen had distributed throughout all the tissues in a certain part of the plant, it gradually decreased.
