Ultrastructure ofDatura stramoniumInfected with an Euphorbia Virus Suggestive of a Whitefly-Transmitted Geminivirus

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Abstract
Inoculation of D. stramonium with an Euphorbia virus in raw leaf sap from wild Euphorbia heterophylla (which occurs widely in southern Florida [USA],), caused chlorotic lesions on inoculated primary leaves and mosaic or mottling on newly developed leaves. Thin-section electron microscopy of infected leaves revealed that the ultrastructural changes resembling those caused by whitefly-transmitted geminiviruses were greatly enhanced. These included the segregation of nucleolar components into discrete fibrillar and granular regions and the occurrence of fibrillar bodies in the nucleoplasm associated with isometric viruslike particles 15-18 nm in diameter. In addition, certain cytopathic effects not common to other whitefly-transmitted geminiviruses were observed: the infection was not limited to phloem cells, and the occurrence of cytoplasmic inclusions surrounded by rough endoplasmic reticulum and Golgi bodies. In leaf dip preparations, viruslike particles appeared predominantly in pairs, which is typical of other geminiviruses. The Euphorbia virus probably belongs to the group of whitefly-transmitted geminiviruses.