Karyotypic changes in potato plants regenerated from protoplasts

Over two hundred plants were regenerated from shoot-culture derived proto-plasts of potato (Solanum tuberosum L. cv. Majestic). Some had grossly aberrant phenotypes but the majority were similar to, or indistinguishable from normal control Majestic. Cytological examination showed that on average, 57% of the regenerants had the normal chromosome number (2n=4x=48). The remainder were aneuploids and fell into two classes in approximately equal numbers. The first class was limited at about the euploid level (ie, 2n=44−49). The second class contained plants with higher chromosome numbers ranging from 2n=73 to the octaploid level (2n=8x=96). The overall results represent an improvement over our earlier studies on chromosome variation in protoplast-derived potato plants. In addition, three cases of structural chromosome variation were observed.