Validation of cryopreservation protocols for plant germplasm conservation: a pilot study using Ribes L.

Uniformly applicable techniques for germplasm preservation are important to the international genetic resources community and validation of techniques among working genebanks will enable the integration of new technologies into plant genetic resources programs. Apical meristems from micropropagated plants of Ribes nigrum L. cv. Ojebyn and R. aureum cv. Red Lake were used to test three cryopreservation protocols (controlled freezing, plant vitrification solution no. 2 (PVS2) vitrification and encapsulation–dehydration) at the USDA-ARS National Clonal Germplasm Repository (NCGR), Corvallis, OR, USA and the University of Abertay Dundee (UAD), Scotland. Similar results were obtained with PVS2 vitrification at both locations but meristem regrowth varied greatly for the other techniques. Variable results between the locations were noted for controlled freezing and were largely attributed to differences in ice crystal initiation by the controlled rate freezers. Low survival of `Red Lake' at UAD with all three techniques was attributed to poorly performing shoot cultures. Attention to protocol details is important for limiting variation between locations and step by step instructions for procedures and solution preparation aided protocol standardization. These studies suggest that source plant status, cryogenic facilities, and culture conditions may be the most likely causes of variation when validating cryopreservation methodologies in different locations. However, in-house optimization of standard procedures offers considerable potential in ensuring that cryopreservation methodologies can be transferred between international laboratories.