In vitro plant regeneration of Ocimum basilicum L. is accelerated by zinc sulfate

This article describes a fast, simple, and efficient plant regeneration protocol for Ocimum basilicum L. Two sets of experiments were performed. The first set was performed on Murashige and Skoog (MS) medium lacking zinc sulfate heptahydrate (ZnSO4·7H2O) and containing varying concentrations of indole-3-acetic acid (IAA). The second set used three different concentrations (8.6, 12.9, and 17.2 mg L−1) of ZnSO4·7H2O along with varying concentrations of IAA. In the first set, without zinc sulfate, an IAA concentration of 1.0 mg L−1 (MS4) was found to be most effective, producing a mean of 12.6 roots per hypocotyl explant, while shoots were not produced. In the second set, with zinc sulfate, a combination of 12.9 mg L−1 ZnSO4·7H2O + 1.0 mg L−1 IAA (MS11) produced significantly more shoots per explant (15 shoots) than a combination of 12.9 mg L−1 ZnSO4·7H2O + 0.5 mg L−1 IAA (MS10), which produced only six shoots. Later, the plantlets were successfully acclimatized (100%) and finally transferred to the greenhouse (ex vitro). In the O. basilicum plants grown using MS11 medium, total phenolic content and rosmarinic acid content were estimated from stem, shoot tip, and old leaf tissue of in vitro plantlets, ex vitro plantlets, and flowering plants. The highest amounts of total phenolic content (131.8 mg gallic acid equivalent g−1 DW) and rosmarinic acid (13.0 mg g−1 DW) were obtained in the old leaf tissue at flowering time. This rapid regeneration protocol for O. basilicum L. represents a major improvement over the conventional protocols for plant regeneration and propagation of this species.