Somaclonal variation in tuber disc-derived populations of potato : I. Evidence of genetic stability across tuber generations and diverse locations.

Approximately 1,600 potato (Solanum tuberosum L.) plants of the cultivar 'Superior' were regeneratedin vitro from meristems adventitiously initiated on tuber disc expiants. Direct regeneration from tuber disc cells, by passing a callus intermediary, is efficient and results in low frequencies of plants with gross phenotypic aberrations. The somaclonal plant population was statistically characterized in field plots over five asexual generations and in three diverse locations. When compared in advanced generations to a large population of control plants propagated from stem cuttings, the means of the somaclonal population were significantly different, often shifted in the desirable direction, for 16 of 22 horticulturally important traits. Somaclonal population variances statistically exceeded those of the controls for 13 of the 22 traits. Regressions between consecutive tuber generations and between locations or replications (blocks) within a generation were significant in the somaclonal population for all traits analyzed. In a few instances, significant control population regressions occurred that are interpreted to be the result of non-random, non-genetic factors primarily affecting control plants of low vigor. Selected somaclones exhibiting desirable alterations for yield, tuber number and shape, and vigor were stable over more than two consecutive asexual generations.