Somaclonal variation in potato: a karyotypic evaluation

The data on somaclonal variation in potato are reviewed and discussed from a karyological point of view. Potato species are polysomatic. This pre-existing genetic variation is introduced into in-vitro cultures. Cultures of protoplasts, cell suspensions and calli show a high degree of nuclear instability leading to polyploidy, aneuploidy and structural chromosome alterations. Genetic and tissue culture factors influence the degree of instability. In-vitro cultures showing gross karyotypic changes have a decreased capacity to regenerate into whole plants. Cell selection takes place during the regeneration process, but most of the regenerated plants still show karyotypic alterations, which have most probably arisen before and during the in-vitro culture period. These alterations coincide with phenotypic variation and chimeras among the regenerated plants.