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.
Highlights
Irish potato (Solanum tuberosum) is an important staple food crop as well as a cash crop in the highland areas of Uganda where it is grown by over 300,000 smallholder households
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
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’
Summary
Irish potato (Solanum tuberosum) is an important staple food crop as well as a cash crop in the highland areas of Uganda where it is grown by over 300,000 smallholder households. The establishment of in vitro reproducible regeneration protocols for cell suspension cultures in economically important potato cultivars provide an opportunity to make Biotechnology applications such as genetic engineering techniques more successful (Hussain et al, 2005). Use of in vitro techniques such as somatic embryogenesis and regeneration combined with genetic engineering hold great prospect in addressing some of the production challenges for this crop especially diseases and seed quality (JayaSree et al, 2001). Due to differences in regeneration abilities of cultivars that are recalcitrant to various biotechnological advances (Sharma et al, 2008; Kumar and Kumar, 1996), identification and screening of useful cultivars for embryogenic callus formation and subsequent plant regeneration using in vitro cell culture, forms the key steps in potato genetic improvement program (Hoque et al, 2007). This study was conducted to establish and optimize a regeneration system for two agronomically important potato cultivars (‘Victoria’ and ‘Rutuku’)
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