Ploidy levels in leaf callus and regenerated plants of Solanum tuberosum determined by cytophotometric measurements of protoplasts.

In potato (Solanum tuberosum) instabilities in nuclear DNA content in callus cells of a monohaploid and a dihaploid and in tuberprogenies of a regenerated, doubled dihaploid plant were assessed by cytophotometry in isolated, purified protoplasts. Leaf protoplasts of a tetraploid variety have nuclei with 3.6±0.08 pg of DNA. In callus protoplasts a dihaploid showed 3 and a monohaploid 6 ploidy levels. Progeny of a plant, doubled and regenerated from dihaploid callus, showed mixo-euploidy, indicating an instability similar to the dihaploid callus; in addition, there are mixo-aneuploid cells.These findings confirm and extend earlier observations based on chromosome counts in other genotypes of potato. The experimental approach can be applied to a variety of other purposes.