An efficient and reproducible plant regeneration protocol for the South African sweet potato (Ipomoea batatas Lam.) cultivar Blesbok was developed in this study. The effect of different hormone combinations and type of explant on shoot regeneration was evaluated in order to optimize the regeneration protocol. Explants in the form of stem sections, leaf discs, apical shoots and axillary buds derived from in vitro stock plant cultures were cultured on Murashige and Skoog (MS) media supplemented with 36 combinations of naphthalene acetic acid (NAA) (0, 0.01, 0.1, 0.2, 0.5, and 1 mg/L) and 6-benzylaminopurine (BAP) (0, 0.01, 0.1, 0.2, 0.5 and 1 mg/L). The highest percentage of shoot regeneration was obtained when apical shoot explants (31%) and axillary bud explants (22%) were cultivated on MS supplemented with 0.01 mg/L NAA + 1 mg/L BAP. Leaf discs and stem section explants produced highly recalcitrant callus that did not regenerate into shoots in shoot induction medium (SIM). Callus from apical shoots explants cultured on SIM developed into shoots. The shoots rooted readily on root induction medium (RIM) and then in hormone free MS medium. Regenerated plants appeared normal and showed a 100% survival rate when transferred to soil. The regeneration protocol described in this study will be used in a plant transformation protocol to produce transgenic sweet potato with broad virus resistance.
Key words: Tissue culture, regeneration, sweet potato, genetic transformation.
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