Effect of culture medium on the small-scale vegetative propagation of the res seaweeds, Gracilaria changii and Gracilaria edulis

Abstract

This study examines the ability of Graci/aria changii and Graci/aria edulis to propagate vegetatively from thallus segments (apical segments, mid segments and basal segments) in different culture media. Graci/aria samples were collected from Middle Banlc, Penang Island and brought back to the laboratory in Universiti Malaysia Terengganu for further cultivation. Culture media chosen were Natural aged seawater, Enriched natural seawater (ES) medium and Plymouth Erd-schreiber (PE) media with soil extracts prepared from soil samples obtained from Sandakan, Setiu Wetland and Garden soil. Effects of culture media on Graci/aria segments were observed and expressed in the form of number of branches, length of newly formed branches and specific growth rate ( compiled as daily growth rate and weekly growth rate). Cultivated apical segment in all media showed overall elongation rather than branch formation while mid and basal segments showed the opposite. Highest branch number for all cultivated segments of Graci/aria changii was observed in PE (Garden Soil) medium (16 on apical segments, 80 on mid segments and 85 on basal segments). As for Graci/aria edulis, all highest branch numbers were observed in Natural aged seawater: 229 branches were recorded for apical segments, 268 on the mid segments and 242 on the basal segments. In terms of branch length, longest branches were observed in ES medium and recorded as 9mm (apical segments), 9mm (mid segments) and 10mm (basal segments) for Graci/aria changii; 18mm (apical segments), 27mm (mid segments) and 23mm (basal segments) for Graci/aria edulis. Generally, it was observed that ES medium and PE (Setiu) medium provided the best results for most of the segments. Highest specific daily growth rate based on fresh weight recorded in ES medium were 0.0096 day"1 for Graci/aria changii apical segments, 0.0155 day °1 and 0.0149 day·1 for Graci/aria edulis mid and basal segments respectively. As for the PE xiii (Setiu) medium, the highest daily specific growth rate observed were 0.0033 dal and 0.0034 day-1 for Graci/aria changii mid and basal segments respectively, and 0.0275 day-1 for Graci/aria edulis apical segments. The highest daily specific growth rate based on length was highest in ES medium for both Graci/aria changii and Graci/aria edulis (0.0084 day"1 and 0.0105 day"1 respectively). Thus, ES medium and PE (Setiu) medium are suitable for culture purposes in laboratory.