Ultrastructural events during hypersensitive response of potato cv. Rywal infected with necrotic strains of potato virus Y

Potato plants cv. Rywal with hypersensitivity gene Ny-1 infected with PVY^N or PVY^NTN reacted in local necroses 3 days after infection. Potato virus Y (PVY) particles were found in epidermis, mesophyll, phloem and xylem cells in inoculated leaves. Noncapsidated virus particles (without capsid protein) were observed already 10 h after infection by using electron microscopy in situ. Capsid protein on one terminus of noncapsidated virus particles was located 5 days after inoculation with the use of immunogold labeling method. Whereas cytoplasmic inclusions were observed for the first time 24 days after infection during hypersensitive response. Ultrastructural studies showed that ER may take part in PVY RNA replication and capsidation of Potyvirus particles. Observed cytopathological changes and virus particles indicate that cell nucleus and mitochondrion might participate in PVY life cycle. During hypersensitive response PVY particles were found in plasmodesmata as well as in phloem and xylem.