title: Development of a PVS2 droplet vitrification method for potato cryopreservation.
abstract: BACKGROUND
  CIP maintains the largest in vitro clonal potato collection in the world, comprising 4,013 landraces and 3,353 improved accessions. The in vitro technology is more efficient and secure than conservation in the field, allowing in vitro plantlets to be stored for approximately 2 years without sub-culture. This method however is not ideal for the long-term germplasm conservation because it is labor consuming, costly, and carries risks of losing accessions due to human error, such as contamination and mislabeling during sub-culturing.
  
  
  OBJECTIVE
  To improve the potato cryopreservation procedure based on the droplet PVS2 vitrification.
  
  
  METHODS
  The improved method is as follows: excision of 1.8-2.5 mm apical shoot tips from 3 weeks old cultures; 15 min exposure to a loading solution and 50 min to PVS2 (at 0 degree C); ultra-rapid cooling on aluminum foil strips (0.5 x 2 cm) in LN; rewarming (20 min) in 1.2 M sucrose MS liquid medium; post-cryo culture in the dark on potato meristem medium with progressively decreased sucrose levels (daily transfers from 0.3, to 0.2, to 0.1 M and maintained on 0.07 M). This method was compared with those previously applied by IPK (Germany) and CIP potato genebanks.
  
  
  RESULTS
  Survival and recovery were higher using the PVS2 droplet method. Cultivars from several species, one frost tolerant (Solanum juzecpzukii, cv. Pinaza) and two drought tolerant (S. tuberosum subsp andigena, cv Ccompis, and Solanum spp, cv Desiree) responded similarly.
  
  
  CONCLUSIONS
  The improved method is recommended for the long term conservation of diverse potato germplasm.
authors.affiliation: International Potato Center (CIP). Apartado 1558, Lima 12, Peru. A.panta@cgiar.org.
authors.forename: A
authors.initials: A
authors.lastname: Panta
authors.affiliation: Bioversity International, Willem de Croylaan Leuven, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Panis
authors.affiliation: International Potato Center (CIP). Apartado 1558, Lima 12, Peru.
authors.forename: C
authors.initials: C
authors.lastname: Ynouye
authors.affiliation: Bioversity International; Department of Biosystems, KU Leuven, Willem de Croylaan, Leuven, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Swennew
authors.affiliation: International Potato Center (CIP). Apartado 1558, Lima 12, Peru.
authors.forename: W
authors.initials: W
authors.lastname: Roca
mesh_terms: D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents / Q000378:metabolism; D004121:Dimethyl Sulfoxide / Q000378:metabolism; D018520:Plant Shoots / Q000502:physiology*; D011198:Solanum tuberosum / Q000502:physiology*; D013395:Sucrose / Q000378:metabolism; D058989:Vitrification
chemical_list: D003451:Cryoprotective Agents; D013395:Sucrose; D004121:Dimethyl Sulfoxide