Growth in microculture of single tobacco cells infected with tobacco mosaic virus.

Single tobacco callus cells with or without tobacco mosaic virus inclusion bodies from systemically infected Nicotiana tabacum plants were grown in microcultures. The culture medium consisted of mineral salts and sucrose; it also contained coconut milk. Out of 100 inclusion-bearing cells and 150 inclusion-free cells, 10 and 70 cultured cells divided; eventually 5 and 65 cells, respectively, formed single cell clones. The 5 clones derived from inclusion-bearing cells, and all but 3 of 40 clones from inclusion-free cells, showed virus inclusions in somne cells. The virus could not be detected in three inclusion-free clones by local lesion assay. The results suggest single-cell culture methods for differentiating virus-free plants from cells of pathogen-infected plants.