Plant tumor reversal associated with the loss of marker chromosomes in tobacco cells.

In single cell clones from a tumorous tobacco strain and in plants regenerated from them, decrease or loss of tumor virulence is associated with the decrease or elimination of specific marker chromosomes. Cells without marker chromosomes called "normal cells", are obtained. Plants regenerated from strongly tumorous clones are obtained either from a mixed population of normal and weakly-tumorous cells or from normal cells only. In the first case, plants are weakly tumorous and in the second they are non-tumorous, like the check sample. Plant tumor reversal could be explained by such a mechanism.