Tissue culture of brown seaweed

Abstract

The harvesting of macrophyte algae (seaweeds) is well established and on a world-wide scale more than 180,000 tonnes dry weight of algae such as the phaeophytes Laminaria, Undaria,Sargassum and Macrocystis, the red algae Eucheuma, Gracilaria and Porphyra, and the green algae Ulva, Monostroma and Caulerpa are harvested annually. Much of this algal biomass comes from farmed rather than wild species. The red and brown algae are the source of the phycocolloids agar, alginate, agarose and carrageenan which are of fundamental importance to the development of biotechnology; i.e. for the culture of microorganisms (agar), for the separation of biomolecules (alginate and agarose) and for the production of food products (agar, carrageenan, alginate). The successful large-scale cultivation of these algae requires, amongst other things, the ability to select fast growing and disease resistant strains which produce large quantities of the desired phycocolloid. To this purpose classical plant breeding programs are being carried out, however these are slow and the production of superior cultivars takes much time and effort (Van der Meer 1988). In recent years there has therefore been much interest in developing protoplast and tissue culture systems which would allow more rapid selection and propagation of suitable cell lines, the possibility of producing hybrids by cell fusion and new strains by genetic engineering (Polne-Fuller and Gibor 1987b, Le Gallet al. 1990). Work in our laboratory has concentrated mainly on the brown algal genera Ecklonia and Cystophora. Ecklonia was chosen because it is easily obtained and is a potential source of alginate, and Cystophora, a genus endemic to Australia and New Zealand, because previous studies indicated that this genus appears to be a good source of tocopherols and tocotrienols (Gregson et al. 1977, Kazlauskas et al. 1981, unpubl. results). The tocopherols are of interest and also provide a convenient model for the study of the production of secondary metabolites in algal tissue culture. In this paper we describe some of our findings on the tissue culture of these species and on their tocopherol content