Cytopathological potato virus Y structures during Solanaceous plants infection.

The ultrastructural analysis of tobacco, potato and pepper tissues during infection with necrotic strains and the ordinary Potato virus Y strain of revealed the presence of virus inclusions not only in the epidermis and mesophyll but also in the vascular tissues. For the first time cytoplasmic inclusions were documented in companion cells and phloem parenchyma as well as in xylem tracheary elements. The ultrastructural features studied in this work consisted of mostly laminated inclusions (in the traverse and longitudinal section), which were frequently connected with enlarged cisternae of endoplasmic reticulum (ER) located in the direct vicinity of the cell wall attached to virus particles opposite to plasmodesmata. It was noticed that ER participates in synthesis and condensation of the PVY inclusions. During compatible interaction of tobacco and potato plants with PVY, amorphous and nuclear inclusions were observed. Such forms were not found in pepper tissues and potato revealing the hypersensitivity reaction to the infection with PVY necrotic strains. It was stated that the forms of cytoplasmic inclusions cannot serve as a cytological criterion to distinguish the potato virus Y strains and do not depend on host resistance level. Only in compatible interaction in Solanaceous plants tissues cytoplasmic inclusions were observed from the moment the morphological symptoms appeared. In the reaction of hypersensitivity, the inclusions were found on the 24th day following the infection with the PVY necrotic strains, whereas the symptoms were observed 3 days after the PVY infection.