Somaclonal variation in minima descriptors of tuber in potato/ Variacao somaclonal nos descritores minimos de tuberculo em batata

In potato, tissue culture is used to retrieve cultivars infected by viruses, however, in vitro culture can lead to somaclonal variation. This study aimed to identify somaclones and evaluate the effect of type of explant and subculture time on the occurrence of somaclonal variants in cultivars 'Asterix ' and 'Macaca'. Tubers produced in plants regenerated by direct and indirect organogenesis of shoot apical and nodal segments derived from the culture of shoot tips of clones in subculture for 12 (young clone) or 70 (old clone) months in nutritive medium MS and cultivated in field were assessed in six minima descriptors of the potato. The averages were compared to patterns described for the cultivars and somaclones were considered only those that were framed in a different phenotypic class from standard of cultivar In 'Asterix ' and 'Macaca ' somaclonal variants were observed in four and two descriptors, respectively, however, only in the tuber shape and flesh color occurred somaclonal variation simultaneously in both cultivars. Moreover, remained stable the depth of the eyes and the greening of the tuber. Somaclonal variants can be identified by use of minima descriptors of tuber. 'Asterix ' and 'Macaca ' are equally susceptible to somaclonal variation. Twelve months of subculture is enough to cause somaclones in both cultivars. Shoot apical and nodal segments derived by direct or indirect organogenesis, are explants equally unstable to the production of seed potatoes. Key words: Solanum tuberosum L., tissue culture, genetic stability. Em batata, a cultura de tecidos e utilizada para recuperar cultivares infectadas por viroses, entretanto, o cultivo in vitro pode conduzir a variacao somaclonal. O presente estudo teve como objetivos identificar somaclones e avaliar o efeito do tipo de explante e do tempo de subcultivo sobre a ocorrencia de variantes somaclonais nas cultivares 'Asterix' e 'Macaca ' Tuberculos produzidos em plantas regeneradas por organogenese direta e indireta de explantes derivados do cultivo de apices caulinares de clones em subcultivo ha 12 (clone novo) ou 70 (clone velho) meses em meio nutritivo MS e cultivadas em campo foram avaliados em relacao a seis descritores minimos da batata. As medias observadas foram comparadas aos padroes descritos para as cultivares e somente foram consideradas somaclones aquelas que foram enquadradas em uma classe fenotipica diferente do padrao da cultivar respectiva. Em 'Asterix' e 'Macaca' ocorreram somaclon