The effect of initial weight of seedlings grafted from tissue-cultured and local strain seedlings on growth and carrageenan content of the Red Seaweed (Kappaphycus alvarezii) using a grafting method

Abstract

A grafting experiment using tissue-cultured and local strain Kappaphycus alvarezii seedlings was conducted from January to April 2019 and consisted of two steps. Firstly, grafting and propagating the seedlings using three different initial weights (IW) of 10, 15 and 20 g. Secondly, a culture experiment using the new seedlings produced from the first step. Seedlings were completely attached to each other after 18 days following the first step with a mean 75.0% grafting rate. The new seedlings were then cultured for 45 days using a long line method. The highest daily growth rate (DGR) was 4.36 %.day-1 obtained from 20-g IW while the lowest DGR was 4.01%.day-1 from 15-g IW. It was found that rapid changes in water salinity and turbidity may affect the success in terms of grafting rate and DGR. The ratio of fresh weight (FW) to dry weight (FW:DW) showed no significant differences among treatments although the 20-g IW showed the highest FW:DW ratio (8.21: 1) followed by 15-g IW (7.87:10) and 10-g IW (6.63:1). In contrast, 10-g IW and 15-g IW showed a significant difference in term of carrageenan content from 20-g IW. The 10-g IW carrageenan content was highest (40.38%) followed by 15-g IW (40.25%) and 20-g IW (38.34%). Salinity was 24-32 ppt, temperature was 29-31 °C. Nitrate and phosphate were 0.324-0.420 mg.l-1 and 0.180-0.538 ppm, respectively, while turbidity range was 3,128-9,336 NTU. In conclusion, for this method of grafting, it is recommended to use 20-g initial weight.