Vegetative Propagation of Dictyota kunthii (Dictyotales, Phaeophyceae) Through Thallus Fragmentation and Ligulae: Potential Alternatives for Cultivation

The growing interest in the commercial exploitation of the bioactive components of <i>Dictyota</i> species, including <i>Dictyota kunthii</i> due to its antifungal activity and use in the development of innovative bioproducts, depends on the availability of biomass. In this context, the cultivation of this species emerges as a promising alternative. This study examined thallus fragmentation and ligulae development as methods to produce <i>D. kunthii</i>. Accordingly, thalli were divided into apical, middle, and basal sections to generate the respective tissue fragments, which were cultured under controlled conditions. On the other hand, ligulae development was studied under different conditions of photon flux density (10, 35 and 65 µmol m^-2s^-1); temperature (10, 17 °C); photoperiod (8:16, 12:12, 16:08 h [Light:Dark]), and seawater enrichment:Basfoliar^®, Compo Expert, Krefeld, Germany and von Stosch solutions. The results show that fragmented thalli were non-viable, exhibiting neither wound healing nor regeneration at the cut sites. Furthermore, no buds or new branches were formed. In contrast, ligulae developed under all tested conditions, with nutrients, light, temperature, and photon flux enhancing apical cell formation and branching. We conclude that ligulae can effectively be used as propagules to cultivate fast-growing, branched <i>D. kunthii</i> plantlets. Accordingly, we recommend using a suspended culture system at 17 °C with a 12:12 (Light:Dark) photoperiod and 65 µmol m^-2 s^-1 light intensity, as well as adding nutrients (Basfoliar^® at 0.1 mL L^-1). Under these conditions, growth rates equal to or exceeding 10% d^-1 can be achieved, supporting the feasibility of scaling up to larger volumes for biomass production.