Development of zygote for seed production of Sargassum swartzii in India

Abstract

Sargassum swartzii is economically exploited in India for alginate production. Indiscriminate harvesting of S. swartzii in natural beds leads to fast depletion. For sustainable utilization of this alga, it is inevitable to undertake its mass cultivation. Therefore, investigations were undertaken to develop a technology that can boost cultivation of this important species. An attempt was made to optimize the culture conditions for developing zygote-derived germlings for artificial seed production through vegetative parts such as vesicles and tertiary leaves. Vesicles and tertiary leaves (n = 90) were subjected to a range of irradiances (05, 25, and 45 μmol photons m −2 s −1 ), salinity (15, 20, 25, 30, 35, 40, 45, 50, and 55 psu), and photoperiod (8:16, 10:14, 12:12, 14:8, and 16:8-h (L/D) regimes under 30-day culture. Maximum regeneration (%) of receptacle from vesicles and tertiary leaf was observed at an irradiance of 45 μmol photons m −2 s −1 , 35 psu salinity, and 12:12-h (L/D) photoperiod which appears to be the most optimal condition. Variations in receptacle regeneration through vesicles and tertiary leaves were highly significant under different irradiances, salinities, and photoperiods (p < 0.05), and there were no significant differences between % regeneration of vesicles and tertiary leaves (p > 0.05). Germlings development followed the eight nuclei, one egg pattern which is quite common in the Sargassaceae. Within a day, multicellular germlings were developed with a bunch of unicellular rhizoids from fertilized oospores through repeated cell divisions. These findings confirmed that vesicles and tertiary leaves can be used as seed stock for the development of artificial seed production in S. swartzii as they contain primordial tissue for receptacle development.