Cytological Alterations in Tissues of Gomphrena globosa Plants Systemically Infected with Tomato Bushy Stunt Virus

Abstract

SUMMARY Special environmental conditions were used to induce systemic infection by tomato bushy stunt virus (TBSV) in Gomphrena globosa. Severe mottle symptoms were followed by the formation of necrotic lesions. The mottled tissue consisted of small patches of necrotic, chlorotic and green tissue closely intermingled. The ultrastructure of such systemically infected G. globosa leaves was investigated. In the mesophyll and bundle sheath cells of the chlorotic patches the chloroplasts were severely altered and often connected to multivesicular (MV) bodies, whose vesicles and vacuoles contained fibrillar material. The MV bodies are thought to originate from chloroplasts and may be involved in TBSV replication. Virus appeared in the cytoplasm and central vacuole as scattered particles or small paracrystalline aggregates. Dark spots, probably proteinaceous material, were present in the cytoplasm. The cells of the necrotic patches appeared completely collapsed and contained virus particles. The necrotic lesions were cytologically quite similar to those produced in hypersensitive conditions.