Ever since human beings first experimented with growing their own food, they have saved seeds for use in future crops. Agricultural technologies and genetic science have advanced since then. Yet it is still necessary to collect, preserve and store the living reproductive material of plants ? called "germplasm," both to improve the crops we grow today, and for the benefit of future generations.

That's the mission of the Plant Genetic Resources Unit in Geneva, New York. It's one node in a U.S. Department of Agriculture-funded network of "seed banks" that holds a vast collection of plant materials. The main federal seed bank, in Fort Collins, Colorado, houses a half million seeds all by itself.

With over 5000 varieties of seeds, cuttings and trees, the Geneva, New York, facility is the largest collection of apple germplasm in the world. "When you're a curator, you want to get the most diverse collection of whatever you're collecting," says Research Director Philip Forsline.

Forsline is equally proud of the collections his colleagues down the hall are responsible for. "They collect, maintain and catalog tomatoes, onion, Brassica crops like cauliflower and some of the Cucurbita like squash, even some small items like celery and buckwheat."

Forsline says that securely archiving the genetic material of all crops is a critical task, especially in the case of the world's major food crops like wheat, soybeans and maize, all of which are grown from relatively few genetic varieties.

"Most of our crops are what you call a 'monoculture,'" he explains. "If some new disease were to come along, it could wipe out most of the crop, because it's so genetically non-diverse. That is the reason it's important to have what are called 'ex situ' collections like this."

Crop quality and health can often be improved by carefully cross-breeding domesticated and wild specimens of the same species. So researchers often go to regions of the earth where a species originated and still grows wild.

For example, because U.S. commercial apple trees are often felled by diseases like "fire blight" and "apple scab," Forsline and his team have made several field trips to the forests of Kazakhstan, where the apple originated, to collect wild apple seeds. Because this fungal disease co-exists with ancient wild apple trees, Forsline concludes that the trees have evolved genetic resistance to it.

"We'll find the resistant ones and introduce them into our collection and make the seeds available to breeders to improve the apple so we'll have scab-resistant apples."

Most of the seeds at the Geneva facility are stored in huge walk-in freezers kept at minus 20 degrees Celsius. "That way," says Larry Robertson, the Geneva seed bank's vegetable curator, "we can keep our seed up to 100 years, depending on the crop."

Robertson's main job is germinating and cultivating seed samples. If a seed sprouts, it shows the stock is still viable. Plant breeders routinely request samples of these viable seeds from the facility and experiment with new genetic strains that produce plants with new traits.

Organic farmers especially treasure the facility's resources, which can help produce esthetically pleasing and marketable produce, such as elegantly striped lettuce, for example, as well as heartier and more nutritious vegetable specimens.

Robertson says last year alone, the Plant Genetic Resources Unit sent out 5000 seed samples, 40 percent to breeders and researchers abroad. South Korea got a large variety of onion seeds, for example, and Turkey received valuable germplasm for crops such as cabbage, cauliflower and broccoli.

Because plant diversity is key to our survival, it is essential that plant germplasm be protected and shared. If germplasm is lost, it cannot be recreated and so is lost forever.

"You think of air and water and energy as resources," says Forsline, "but germplasm is just as [valuable] a resource as they are. It is the bare bones of our food supply. It is a legacy and a resource for all of mankind now, and for the future."

Boosted in part by alarm over climate change, and the ongoing destruction of many of the earth's natural plant habitats, a worldwide movement to preserve this resource seems to be growing. The world's largest germplasm repository, called the Svalbard Global Seed Vault, is scheduled to open in Norway next year.