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High throughput culture and gametogenesis induction of Laminaria japonica gametophyte clones

Zhang, Quan Sheng, Qu, Shan Cun, Cong, Yi Zhou, Luo, Shi Ju, Tang, Xue Xi
Journal of applied phycology 2008 v.20 no.2 pp. 205-211
Laminaria, Saccharina japonica, bottles, clones, correlation, eggs, females, gametogenesis, gametophytes, light intensity, males, mixed culture, models, photoperiod, sporophytes, China
In anticipation of the application of a new sporeling-raising method using gametophyte clones to Laminaria commercial cultivation in China, techniques of mass culture and gametogenesis induction of L. japonica gametophyte clones were developed, as a mass of fertile gametophytes is a prerequisite for sporeling-raising with the new method. Gametophyte clones which were subjected to fed-batch culture exhibited a classical logistic growth curve. Growth rates decreased gradually after 2 months of culture, and were negatively correlated to cell density. UNOVA also showed that only cell density has a significant effect on the growth of gametophyte clones under the experimental conditions. Based on the dynamics models revealed, a culture strategy only directed at the control of cell density was adopted. By this strategy, a total of 36 kg wet weight from an initial weight of 0.75 kg was achieved after 3 months culture in 100 20-L bottles. The final average density reached 24 g L⁻¹. For the subsequent gametogenesis induction, amplificatory male and female gametophyte clones were cut, mixed and cultured in bottles under the same conditions used in amplification except for a change of photoperiod from continuous irradiance to 10 h light: 14 h dark cycle. Egg discharge occurred 10 days after the mixed culture and increased gradually with the culture duration. Most gametophytes gave rise to sporophytes 20 days after induction. Large-scale culture of gametophyte clones and gametogenesis induction for commercial cultivation in 2003-2005 have been conducted successfully.