Somatic embryogenesis and plantlet regeneration from the seaweed Kappaphycus striatus

Abstract

The seaweed Kappaphycus striatus is a well-known source of carrageenan and other valuable bioactive compounds. To improve the efficiency of propagation of this important natural resource, we studied the aseptic efficiency of silver nanoparticles (AgNPs) in the explant sterilization process. We further evaluated the effects of culture media, plant growth regulators (PGRs), light intensity, and rotary shaking on callus induction and proliferation, somatic embryogenesis, and micropropagules regeneration of the red algae K. striatus. The treatment with AgNPs at a concentration of 500 ppm optimally resulted in the absence of contaminations. A high explant survival rate (80.0%) and callus induction rate (54.4%) were obtained. Healthy calli were transferred separately into MS (Murashige and Skoog), PES (Provasoli’s enriched seawater), and MPI media for callus proliferation. The results indicated that the PES medium was suitable for callus induction with higher yields of fresh and dry biomass (112.00 mg and 11.50 mg, respectively) compared with the MPI medium (79 mg fresh and 6.73 mg dry weight). Calli cultured using the MS medium failed to grow. The optimal condition for callus proliferation was the PES medium supplemented with 1.0 mg⋅L−1 1-naphthaleneacetic acid (NAA) and 1.0 mg⋅L−1 6-benzylaminopurine (BAP). Somatic embryo (SE) induction was best obtained when cultured calli were transferred onto PES semi-solid medium supplemented with 1.0 mg⋅L−1 NAA and 2.0 mg⋅L−1 BAP. To promote plantlet development, SE clumps were placed in PES liquid medium on a rotary shaker at 100 rpm for separating individual embryos. These embryos were collected and allowed to develop under cool white fluorescent tubes at a light intensity of 55 µmol⋅m−2⋅s−1. The regenerated plantlets had a 50% survival rate, light brown in colour and multibranched. The plantlets reached a length of 2 cm after 2 months of culture.