In vitro clonal propagation of Gracilaria salicornia for rapid biomass multiplication and sustainable seedstock production

Abstract Gracilaria salicornia is an economically important agar-producing red seaweed with potential for biomass production and value-added applications. The availability of adequate and consistent planting material remains an important consideration for the expansion of its cultivation. This study evaluated a liquid modified Provasoli’s Enriched Seawater (PES)-based in vitro culture system for vegetative biomass multiplication of G. salicornia . Healthy apical thallus segments were surface sterilized and cultured under controlled conditions for six weeks. Biomass development was monitored at weekly intervals using relative biomass multiplication, percentage increase in biomass, recorded weekly growth-rate values and qualitative morphological observations. Relative biomass multiplication increased progressively from 1.40-fold after the first week to 5.00-fold after six weeks, corresponding to a 400% increase over the initial biomass. The recorded weekly growth-rate values ranged from 20.3 to 27.4%. Biomass accumulation was accompanied by thallus elongation, new shoot development and lateral branch formation, indicating sustained vegetative growth under the tested culture conditions. These findings demonstrate the potential of liquid modified PES medium for the controlled multiplication of G. salicornia from limited starting material and establish a quantitative baseline for further optimization of the propagation protocol. Future studies should evaluate the effects of culture conditions and plant growth regulator concentrations, as well as genetic fidelity, acclimatization and field performance, to determine the suitability of this approach for scalable clonal planting-material production. The study provides a basis for further development of controlled propagation methods to support G. salicornia cultivation.