184 • Technologies To Maintain Biological Diversity 



Table 7-4.— Estimated Costs^ of Conventional 

 and Cryogenic Storage 



^Costs for accession of onion (a species that survives poorly under conventional 

 storage). Savings for ottier crop species— particularly ttiose witti large seeds- 

 may be less dramatic or nonexistent. 



^Assumes storage conditions of -18° C and seed moisture of 4 to 7 percent, 

 under Mrtticti storage life of onion seed is approximately 25 years. 



SOURCE: P.C. Stanwood and L.N. Bass, "Seed Germplasm Preservation Using 

 Liquid Nitrogen," Seed Science and Technology 9:423.437, 1981. 



tise at many locations, particularly in develop- 

 ing countries, and the lack of scientific data 

 on genetic stability of seeds stored cryogeni- 

 cally. Certainly the capacity to use cryogenic 

 technologies should be part of any newly con- 

 structed facility for seed storage. 



Field Maintenance and Centreiled 

 Environments 



Accessions may also be stored as vegetative 

 plants in field collections or controlled envi- 

 ronments e.g., greenhouses (108). This approach 

 may be necessitated by physiological restric- 

 tions on storing seed, by the need to preserve 

 particular combinations of characters or by in- 

 abilities to obtain satisfactory seed samples 

 (81,108). Field collections can preserve the 

 genetic diversity of many aquatic plants; trop- 

 ical species (e.g., coconut, cacao, mango, or rub- 

 ber trees); tropical forest trees; and some tem- 

 perate trees (e.g., oaks)— which all have 

 recalcitrant seeds (28,42,63,64,84). 



Botanic gardens and arboretums maintain di- 

 verse field collections, though many institutes 



focus on a narrow taxonomic group, as men- 

 tioned earlier. Arboretums conserve limited 

 samples of tree and shrub species with very 

 small natural gene pools that are under pres- 

 sure of destruction, or plants with distinctive 

 characteristics (34,69,80). In the United States, 

 establishing a network among botanic gardens 

 and arboretums, facilitated by the newly formed 

 Center for Plant Conservation at the Arnold Ar- 

 boretum at Harvard University, could allow a 

 division of labor and sharing of expertise that 

 would enable more species and more genetic 

 diversity within species to be maintained (34, 

 106). 



Trees in field collections, however, may have 

 been selected for economically important traits 

 and thus may only represent a narrow range 

 of the total diversity available for a species. 

 CAMCORE, for example, collects seeds only 

 from coniferous trees with commercially val- 

 uable trunk characteristics (i.e., tall and straight) 

 (25). Trees in field collections, nonetheless, can 

 be useful sources of seeds for restoration and 

 reforestation projects (8). 



Many clonally propagated crops are main- 

 tained in field collections. Clonally propagated 

 crops include fruit and nut species; many or- 

 namentals, such as roses; and some root and 

 tuber crops important to developing countries 

 (e.g., sweet potato, cassava, and taro). Seeds 

 may be available for many varieties. However, 

 most of these crops are genetically hetero- 

 geneous, and clones grown from their seeds 

 may not retain the particular qualities of the 

 parent plants (e.g., the seeds of a Macintosh 

 apple do not produce Macintosh apple trees, 

 but rather a range of trees that result from 

 recombination of the genes in the Macintosh 

 apple). The Centro Internacional de la Papa 

 (CIP) in Peru, for instance, maintains an active 

 field collection of potato landraces but also has 

 a base collection of seeds from these accessions 

 (50). 



Pollen Storage 



Pollen is not a conventional form of germ- 

 plasm storage, but information is available on 

 preserving pollen for breeding purposes for 



