Initial acytokinesis during leaf protoplast culture of dihaploid and tetraploid Solanum tuberosum and diploid S. bulbocastanum

Leaf protoplasts of dihaploid (2n=2x=24) and tetraploid (2n=4x=48) Solanum tuberosum, rr, and diploid S. bulbocastanum (2n=2x=24) were cultured in liquid medium. The cultures were studied for early karyological changes during their development. Giemsa staining of spread preparations revealed extremely low percentages of protoplasts developing into calli with the parental chromosome number, and high percentages of acytokinetic cells. The nuclear divisions within a cell were synchronous which allowed the occurrence of spindle interaction, resulting in nuclear poly- and aneuploidization. Although polyploidization was also found in uninucleate cells, a major increase in the formation of true-to-type calli would certainly be established by the improvement of early cross wall formation.