Abstract

In vitro somatic embryogenesis and regeneration are important techniques for crop improvement and mass propagation. This study was conducted to establish and optimize a regeneration system for agronomically important potato cultivars (‘Victoria’ and ‘Rutuku’) of Solanum tuberosum L. in Uganda. Completely randomized design experiments were set up at Bioscience East and Central Africa (BecA) Tissue Culture Laboratory for this purpose. Callus induction and plant regeneration were initiated on internodes and leaf segments of the two potato cultivars in vitro on Murashige and Skoog (MS) medium supplemented with different phytohormones that included auxins such as α naphthalene acetic acid (NAA), cytokinins like benzyl amino purine (BAP), gibberellic acid (GA₃), 2,4-dichlorophenoxyacetic acid (2,4-D) and Zeatin at varying concentrations. Callus response depended on the genotype, the concentrations and composition of growth substances. Hormone combination MS + Sucrose 30% + NAA (2 mg/l) + 2,4-D (2 mg/l) + KN (2 mg/l) was found to have the highest callusing rate, that is, 95 and 53%, respectively for internodes and leaf explants. The calli formed from internodes and leaves were friable and soft. The callus colour in all cases ranged from light brown to light cream and in some cases to light green. Shoot bud initiation was observed in all regeneration culture media, with media combination MS + KN (2 mg/l) + Zeatin (2 mg/l) giving the highest shooting rate. The intervening callus phase led to less number of shoot buds for each callus leading to long incubation period. The study showed that it is possible to regenerate potato cultivars (‘Victoria’ and ‘Rutuku’) from cell suspension culture using Murashige and Skoog (MS) medium supplemented with different phytohormones. Combination of MS with NAA + 2,4-D + Kinetin is suitable for callus induction while MS + kinetin and zeatin was better for shoot induction on calli of potato cultivars ‘Victoria’ and ‘Rutuku’.

Key words: Regeneration, somatic embryogenesis, Solanum tuberosum.