Fifteen Years of Cryopreservation in the IPK Genebank - Experience, Conclusions and Outlook

At IPK, routine application of cryopreservation started in the year 1998 on potato and garlic and, in 2006, on mint. Allium pollen is the newest target. Main methods are: DMSO droplet freezing in potato, vitrification in garlic, droplet vitrification in mint, and direct cooling of pollen in Allium. Across the years, some changes in detailed protocol steps were introduced improving the methods. Since more than 25 years, accessions of IPK's Potato Collections have been maintained via in vitro culture. For potato, a protocol including microtuber formation was applied since the beginning with only minimal modifications. Garlic, however, is not amenable to in vitro storage over such long periods and quickly declining quality requires using fresh material. Accumulating endophytic colonisation revealed to be the main obstacle for prolonged use of in vitro plantlets as source for cryopreservation. Further investigations were performed on morphogenesis, tissue water conditions and genetic stability. For potato, studies were conducted analyzing the methylation patterns of different potato cultivars under three different maintenance systems (field, in vitro, in cryo) in 2012. Although this study revealed differences in the methylation status of different single plants of the same genotype these differences could not be traced back to one maintenance system in particular. Hence, it can be stated that in cryo maintenance does not induce additional genetic variation. In mint, no differences between the in vitro source plants and regenerants from cryopreservation were found using RAPDs. Cost estimations were done in potato and garlic. With respect to cost factors, the large potato collection had been prioritized depending on the request frequency so far experienced for the various genetic resources.