Genetic diversity can be preserved ex situ through various techniques. In contrast, species with recalcitrant seeds can be maintained only in situ or in field collections, botanic gardens and arboretums. Even in standards seed banks, the long-term integrity of the germplasm remains in question. Inadvertent selection or unintentional crossing with other varieties may occcur, and plants stored in vitro mutate at relatively high rates. For this reason, ex situ storage should be considered preservation rather than conservation.
Many obstacles remain in the quest to provide a secure source of germplasm.
One is a lack of information. Then too, the high cost of ex situ collections, particularly when seed is stored at very low temperatures, may force some seed banks to cut back or shut down. But the most serious problem associated with ex situ collections involves gaps in coverage of important species, particularly those of significant value in tropical countries. The most worrisome gaps are in the coverage of species of regional importance, species with recalcitrant seeds, wild species, and livestock. Crops of Regional Importance .