CRYOPRESERVATION OF CLONAL GAMETOPHYTIC THALLI OF PORPHYRA (RHODOPHYTA)

Gametophytic thalli of Porphyra were cryopreserved at liquid nitrogen (LN) temperature with a cryoprotective solution in cryogenic vials. Tw o clonal cultures of gametophytic thalli of P. yezoensis (TU-1,2) and a clonal gametophytic thalli culture of P. tenera (TU-3) were successf ully obtained, These gametophytic thalli cultures were clonally mainta ined via monospores in the laboratory. When the thalli were pre-frozen below -30 degrees C without cryoprotectants, the survival rate was lo w. Dimethylsulfoxide (DMSO) considerably decreased cell damage during pre-freezing to -40 degrees C, but did little to decrease the damage u pon rapid cooling to the LN temperature. This problem was overcome by using dextran, polyvinylpyrrolidone (PVP) or Ficoll in combination wit h DMSO. The subsequent survival rate after immersion in LN exceeded 95 %. This technique allows for the long-term and facile maintenance of c lonal culture of gametophytic thalli of Porphyra.