Shoot Tip Cryopreservation of Solanum Tuberosum Germplasm

Liquid nitrogen storage of vegetatively-propagated germplasm collections is the most economic and reliable long-term preservation method for many of these collections. Over the past 11 years, the USDA-ARS National Center for Genetic Resources Preservation (NCGRP) cryopreserved over 100 different potato (S. tuberosum) germplasm accessions originating from six different countries including the United States. In vitro shoot tips of these accessions are currently processed using the droplet vitrification method described by Haeng-Hoon et al. (2006).  Our goal is to place 150 shoot tips per accession into long-term liquid nitrogen storage. In the first years of the program, the post cryo viability was relatively low with 25 to 40% of the cryopreserved shoot tips surviving and growing into plants. With improvements in methodology, shoot tip viability increased from 40 to 100% in some accessions. Genotype specific responses to cryo tolerance were observed. In addition to the liquid nitrogen storage, all potato accessions stored at NCGRP are also maintained in vitro as minitubers, undergoing a periodic shoot initiation and retuberization. The cryopreservation method used for potato germplasm accessions is very efficient; however, research on protocol modifications is still needed to accommodate cryo storage of recalcitrant potato genotypes.