Vegetatively-propagated germplasm is used to retain the exact genetic line (genotype) of a crop, such as a Red Delicious apple. Germplasm is distributed as cuttings or explants rather than seeds. NPGS collections of vegetatively-propagated crops are maintained in field plantings which are vulnerable to insects, diseases and environmental challenges. Frequent regeneration – for example garlic is replanted every year - increases the vulnerability and cost of the collection. One method to back-up vegetatively-propagated germplasm collections uses tissue culture, where plants are grown and maintained in a sterile environment containing nutrients, a carbon source and vitamins. Cryopreservation of very small (1-2mm) meristematic shoot tips or dormant winter buds in liquid nitrogen (-196°C) presents an alternative method for long term storage that reduces the cost of maintaining growing plants. Protocols for tissue culture and cryopreservation are crop and genotype dependent, with few protocols available for NPGS germplasm. NCGRP has been developing and implementing cryopreservation methods for vegetatively- propagated crops for almost two decades.
See protocols for cryopreservation methods used for shoot tips and dormant buds at NCGRP
Number and genera of vegetatively-propagated plants in long-term cryopreservation at NCGRP (as of September 27, 2010).