LOCALIZATION OF POTATO LEAFROLL VIRUS IN LEAVES OF SECONDARILY-INFECTED POTATO PLANTS

Potato leafroll virus (PLRV) antigen was localized by immunogold label ling in semi-thin leaf sections of secondarily-infected potato plants cv. Bintje. Viral antigen was present in all cell types of the phloem tissue, but occurred most abundantly in the companion cells. Detectabl e amounts of PLRV antigen were found only in the sieve elements in vei ns with a large number of infected companion cells. Occasionally, pare nchyma cells were also found to be infected. PLRV was not exclusively limited to the phloem tissue in the infected potato plants, but was al so found in mesophyll cells neighbouring minor phloem vessels. Spread of virus from cell to cell in the mesophyll was not observed. The dist ribution of PLRV in the potato leaf tissue has implications on its ava ilability for acquisition by aphids.