THE EFFECT OF PRE-CULTURE TEMPERATURE TREATMENT ON THE CRYOPRESERVATION OF POTATO SHOOT-TIPS

The International Potato Center’s (CIP) genebank was established following its foundation in 1971. Currently, 4,607 accessions of 7 cultivated potato species are maintained clonally as tuber, in vitro, cryo- and DNA collections in CIP genebank. In January 2008, CIP’s genebank became the first worldwide to obtain an ISO 17025 accreditation for its in vitro germplasm conservation and distribution systems. The cryo-bank is an integrated part of the total genebank safety backup management system. The vitrification protocol developed by Steponkus at Cornell University was applied to 400 potato genotypes, and 121 accessions were successfully cryopreserved. During 2004-2006, with an aim of establishing a cryo-bank for a long-term conservation of potato landraces, research for improving cryo-procedures was conducted and as result a revised PVS2 vitrification method was developed. Currently, the droplet PVS2 vitrification method is the preferred procedure applied to place the 4,607 accessions of cultivated potatoes into the cryo-bank. Testing 434 potato accessions and using both, 6 and 22°C pre-culture treatments, 92% showed recovery frequency of at least 5%; out of them 67% reached at least 20% recovery. This protocol increased the range of genotypes showing positive post-thawing recovery, and rendered suitable for the long-term conservation of widely diverse potato genotypes, with shoot-tips’ recovery rates of 20-100% in two replicated lots of 50 shoot-tips each.