In vitro development of somatic embryo-like micro-propagules and their regeneration into plantlets from pigmented callus of Eucheuma denticulatum (Burman) Collins et Hervey

Abstract

Eucheuma denticulatum is a commercially important tropical red seaweed widely cultivated for the production of carrageenan and bioactive compounds. This study demonstrates an efficient and reproducible protocol for in vitro production of somatic embryo-like micro-propagules and their subsequent regeneration into plantlets from pigmented callus of E. denticulatum. The effects of silver nanoparticles (AgNPs) on both acclimatization and surface sterilization were systematically evaluated. Optimal acclimatization was achieved in Provasoli’s enriched seawater (PES) medium supplemented with 0.05 ppm AgNPs, resulting in sustained positive growth over six weeks, high survival (76.67%), and minimal ice-ice incidence (less than 5%). For surface sterilization, 400 ppm AgNPs for 10 minutes was identified as the optimal treatment, balancing high aseptic survival (72.22 ± 1.92%) with effective microbial clearance. Callus induction was maximized on PES medium solidified with 1.5% agar under light intensities of 5–15 μmol photons m⁻2 s⁻1. The highest frequency of somatic embryogenesis-like (58.89%) occurred on solidified PES medium containing 1.0 mg L⁻1 NAA and 2.0 mg L⁻1 BAP. Isolated somatic embryo-like structures (SEL) were obtained in liquid PES medium on a rotary shaker at 100 rpm. The regeneration of micropropagules from SEL was most successful in full PES medium at a temperature of 24°C, salinity of 35‰, and light intensity of 55 μmol photons m⁻2 s⁻1. Under these optimized conditions, regenerated plantlets exhibited robust morphology with characteristic glossy brown coloration and vigorous branching. This optimized micropropagation protocol offers a scalable approach for clonal production of disease-free E. denticulatum seedlings, providing a viable option for sustainable Eucheumatoids aquaculture while facilitating the exploration for biotechnological applications.