Seedling production in the industrially important agarophyte Gracilaria dura (Gracilariales, Rhodophyta)

The commercial exploitation of seaweeds largely depends on success of consistent biomass production. The present study demonstrates technical feasibility for rapid production of viable seedlings clonally through selective propagation of apical fragments of Gracilaria dura. The highest regeneration was recorded at 25 psu salinity, 5 mu mol photons m(-2) s(-1) irradiance and 25 degrees C where it ranged between 80.83 +/- 3.95 and 28.77 +/- 2.03 %. The percentage growth in vertical polythene-tube-column culture was ranged between 40.298 +/- 27.25 and 55.687 +/- 19.39 % and found to be effective in producing large numbers of seedlings. These seedlings showed fast acclimation to outdoor culture and recorded growth rates of 1.37 to 2.25 % day(-1) after 1 month. The seedlings grew rapidly when outplanted in open sea with growth rates of 3.06-3.29% day(-1), comparable to commercial farming of Kappaphycus alvarezii along the southeast coast of India. The average length of harvested plants was found to be 7.71 +/- 0.89 cm, while fresh weight was 34.60 +/- 9.81 g. Further study to understand seasonal variation in regeneration and growth is imperative to scale-up the methodology for year-round production.