Freeze Preservation of Apical Meristems of Rubus in Liquid Nitrogen

Shoot tip explants from tissue culture plantlets of five Rubus accessions ( Rubus leucodermis Torr. & Gray, R. spectabilis Pursh, R. idaeus L. ‘Heritage’, Rubus spp. ‘Logan Thornless’ and ‘Merton Thornless’) were frozen slowly (0.8°C/min) to -40° and then rapidly to -196° in the presence of cryoprotectants. Following rapid thawing, regrowth as organized apical growth or as callus occurred on agar media. A combination of polyethylene glycol (PEG), glucose, and dimethylsulfoxide (PGD) was the most successful cryoprotectant.