Scaled-up clonal propagule production in Gracilaria dura (Rhodophyta) for sustainable feedstock production and implications for circular economy

The economic potential of the seaweed sector in India, particularly agarophyte farming, has gained significant attention in recent years. This study was aimed to investigate the feasibility of scaled-up clonal propagule production (25,000 batch⁻¹) of Gracilaria dura under semi-controlled outdoor conditions in tanks and out-planting of clonal propagules in the open sea. Furthermore, the growth pattern, survival, and regeneration under tank cultivation and the weight increase, number, and length of adventitious laterals in the clonal propagules under open sea farming along with the projected potential economic viability of this method were assessed. The clonal propagules of 0.5–1 cm were treated with combination BAP 0.25 mg L⁻¹ for 60 min followed by 1 g L⁻¹ seaweed extract Ascophyllum marine plant extract powder (AMPEP) for 60 min and then KIN 0.25 mg L⁻¹ for 30 min before being cultured for 112 days. Following this treatment, the weight of the clonal propagules increased from 1190 to 1383 g; 100% regeneration was achieved by the 28th day, while a survival of 87.99% was recorded at the end of the experiment on the 112^th day. The average number of adventitious laterals was 3.75 ± 0.4 clonal propagule⁻¹, while the average length of adventitious laterals was 0.93 ± 0.03 cm clonal propagule⁻¹ at the end of the experiment on the 112^th day. Out-planting of clonal propagules was successful, and average weight increased from the initial 126.33 ± 14.65 to 147.5 ± 13.11 g net bag⁻¹ with an average number of 4.0 ± 2.2 adventitious laterals clonal propagules⁻¹ measuring approximately 4.0 ± 1.2 cm clonal propagule⁻¹ in length during the 30-day cultivation cycle was reported. The preliminary projected potential economic analysis of this project demonstrated a net income of USD 109.25–USD 1706.76 year⁻¹ for the industry based operation while same was USD 582.74–2180.25 year⁻¹ for the farmer-based operation. This study contributes towards valuable insights into a scaled-up operation, providing a basis for the circular economy of agarophyte farming in India.