Tubular Inclusion Bodies in Plants Infected with Viruses of the NEPO Type

SUMMARY Tubular inclusion bodies containing single rows of virus particles were observed by electron microscopy in hosts infected with three NEPO viruses. When Nicotiana rustica L. plants were inoculated with cherry leaf roll virus tubules were found in axillary buds 4 days later and reached a maximum concentration after 2 to 3 weeks. Tubules were also found in root tips, pollen, ovules and mature seeds of these plants, but not in the leaf tissue. Sections through cherry leaf roll virus infected tissue showed the tubules to be most frequent in the cytoplasm of undifferentiated cells. They occurred singly or in bundles and appeared to pass between cells. The tubule wall usually consisted of a single layer forming a complete tube in cross section.