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The first long-term studies of seed survival during liquid nitrogen storage were initiated in 1977. Lettuce seed harvested in 1970 and assayed in 1999. Seeds were stored under conventional conditions (top) or split in 1986 and placed in liquid nitrogen vapor (bottom). Viability was maintained under both conditions, but cryogenically stored seeds grew slightly faster. Lettuce seeds sealed in differential scanning calorimetry pans are used to estimate molecular mobility from measurements of heat capacity at liquid nitrogen temperatures. Seed storage in liquid nitrogen

How cells behave at liquid nitrogen temperatures is critical to preservation technology and genebanking, yet it has never been measured. Molecular mobility and changes in viability of cryogenically-stored seeds were measured and longevity was predicted from models based on Avrami kinetics. The mathematics developed for these assays provide the first true indication of life expectancy under cryogenic conditions for any life form. Further development of this technique is likely to provide a non-invasive tool to predict aging kinetics during storage.
More information: Biophysical and physiological aspects of seed development and quality.
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Shoot tips excised from garlic bulbs are soaked in protecting solutions before cryo-exposure. Healthy cultures of sweet potato are used to produce shoot tips for cryogenic storage. Winter buds of apricot are tested for survival to liquid nitrogen temperatures following slow cooling to –30C. Cryopreservation of vegetative tissues

Germplasm for many species cannot be safely genebanked because there are currently no methods that enable cells from these species to survive desiccation or low temperatures. Cryopreservation protocols for species in vegetatively-propagated collections (willow, garlic, sweet potato, cherries and apricots) were developed. Methods will now be tested using genetically-representative subsets of NPGS collections, and if successful, germplasm for these species will be safely preserved in genebanks.
More information: Cellular and Molecular Aspects of Plant Cryopreservation and Cryobiology of Vegetatively Propagated Germplasm
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Texas wild rice seldom flowers or produces seed when it grows in river. Texas wild rice plants are grown in greenhouses to produce seeds. Seeds from Texas wild rice are recalcitrant, but 70% can survive cryopreservation after soaking in exogenous protectants. Genetic diversity in situ and ex situ

The genetic diversity and changes in genetic variation at each step in the genebanking process (collection, maintenance of refugia, production of seed, and cryopreservation) has been quantified for a wild relative of rice, Zizania texana (Texas wild rice). The study provides a model of how to quantify genetic diversity and genetic changes during genebanking that will be used for subsequent wild-collected germplasm.
More information: Population genetics and genomics and Biophysical and physiological aspects of seed development and quality.
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Garlic genetic relationship study imagesGenetic relationships among garlics

Genetic resources of garlic are currently held in field collections not genebanks. Understanding the diversity within the garlic collection is the first step in identifying candidate accessions for preserving in genebanks. Using AFLP fingerprinting methods, we have determined genetic distances of 211 NPGS garlic accessions as well as commercially available types. We found that about half of the NPGS collection is nearly identical. We also found that the genetic relationships were highly correlated with a phenotype-based classification system used by growers.
More information: Population genetics and genomics and Cellular and Molecular Aspects of Plant Cryopreservation.
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