Ecoscience: Preserving Genetic Diversity With Seed Banks

Find out the benefits of seed banks, including the need for genetic diversity and the problems that seed banks face with underfunding.

| May/June 1982

Humankind is fortunate that the extreme seriousness of the loss of genetic variability of crops is balanced by the relative ease with which the situation could be improved. "Seed banks" can, you see, be used to preserve samples of diverse crop strains, as well as populations of their wild relatives. The seeds of most species will keep in cold storage for a number of years before the majority of those in each sample die. Every few years, then, it's necessary to sow the saved seed, allow the plants to mature and harvest the seeds once again for storage.

The Need For Genetic Diversity

However, although seed banks are simple in principle, their operation requires skill and care. The preservation of samples often amounts to little more than allowing the process of natural selection to choose those seeds that most readily survive the storage conditions. Unfortunately, seeds that survive well in storage don't necessarily produce plants with the characteristics that are most useful to farmers.

The rate that a plant strain undergoes selection for survival in storage can, however, be retarded by frequent planting out. But it’s also important that seeds be planted in the region from which they came… or at least under conditions very similar to those that occur in the home area. Otherwise, the strains will lose their unique characteristics, because — once again — selection will gradually adapt them to their new environment.

Seed Banks Are Underfunded

A recent survey, conducted by the government's General Accounting Office (GAO), found that seed-bank operations in the United States leave much to be desired. Our nation's main facility is the Department of Agriculture's National Seed Storage Laboratory at Fort Collins, Colo. Smaller collections are held by various federal and state experiment stations and by commercial seed companies.

The Fort Collins laboratory is currently filled to capacity. It contains more than a quarter-million stored seed samples, but only about half are catalogued so that they're accessible to plant breeders, and the information on many samples is inadequate. Worse than that, the refrigeration equipment suffers periodic breakdowns, and funds aren't available for growing out the seeds as frequently as that should be done.

For example, the bank's large collection of seeds home guayule, a plant with high potential as a new source of natural rubber, hasn't been planted out since World War II, and it's very likely that all of those seeds have died by now. Indeed, well under half of the seeds of any planting from the facility's collections normally germinate, since they've had to endure too long a wait before being sown. Such low survival rates, of course, imply strong selection for storage characteristics.

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