CYTOPATHOLOGY AND ULTRASTRUCTURE OF SOME AFRICAN ISOLATES OF MAIZE STREAK AND SUGARCANE STREAK VIRUSES

Samples of maize leaves naturally infected with maize streak virus (MS V) from Malawi and South Africa, as well as sugarcane leaves naturally infected with sugarcane streak virus (SSV) from Egypt, were examined by light (LM) and transmission electron microscopy (TEM). Intranuclear inclusions, detectable by both methods, were found mainly in mesophyl l and bundle sheath cells, and less frequently in vascular parenchyma and immature phloem cells. At higher TEM magnifications, these inclusi ons consisted of crystalline or noncrystalline aggregates of isometric geminivirus-like particles (VLP) that occurred either singly or in ge minate arrays. Cytopathological changes in these cells were confined t o the nuclei, which were usually larger than normal, with peripheral c hromatin and nucleoli. The nuclear envelope of some inclusion-containi ng nuclei was ruptured, and occasionally a crystal of VLP was found in the cytoplasm of cells in which no intact nuclei were detected. No di fferences in cytopathology were found between MSV and SSV, or between the two MSV isolates examined.