An important aspect of conserving plant genetic resources is having a safe, secure backup. In
a given year, the National Laboratory for Genetic Resources Preservation (NLGRP for short) receives
fifteen thousand to twenty thousand backup seed samples that need to be secured in long-term
storage. It's important to secure samples in two or three geographically separate locations so we
do not lose valuable germplasm in a fire, flood, or other catastrophic event that might occur.
Most of our samples come from USDA genebanks. These genebanks and our lab are part of the USDA-
Agricultural Research Service- National Plant Germplasm System (NPGS for short).
NPGS genebanks back up their collections at NLGRP. Germplasm unique to the United
States is also backed up at the Svalbard Global Seed Vault in Norway. Botanical gardens,
non-governmental organizations, tribal nations, and genebanks around the world also rely on us
for securing their duplicate collections. Our lab also serves as a depository for voucher samples
of newly developed varieties that have received certificates from the Plant Variety Protection
Program or the Journal of Plant Registration. These materials will be stored at NLGRP for five
to twenty years before becoming available through the NPGS. Under the red roof of NLGRP, one of the
world's largest collections of agricultural plant biodiversity is securely stored. We have almost
a million accessions representing ten thousand taxa, and most of this material is stored as seed.
Before seed samples are placed in cold storage they need to be carefully processed to ensure
they remain viable for as long as possible. Let's take a look at how we prepare seeds for storage.
First we need to ensure they are optimally dried so they stay viable in cold storage for
as long as possible. Our drying rooms are at 41 degrees Fahrenheit (5 degrees Celsius) basically
the temperature of your refrigerator at home; however, a dehumidifier keeps the humidity low,
around 25 percent. After two to four weeks in this room seeds are tested to confirm they are
dry enough to store. As the seed is drying we also examine seed health to ensure samples have
high viability. Healthy, properly-dried seed remains alive for a long time in a freezer at
0 degrees Fahrenheit. Once dry, the next step is to weigh the sample, get a total seed count, and
record the storage location. This is done using the GRIN-Global database. GRIN-Global is special
genebanking software that allows us to manage all aspects of managing a genebank collection.
Seed is then packaged in moisture-proof, foil laminate bags that are heat sealed to
keep moisture out. Seed packets are placed into trays and are ready to be stored in the vaults.
The precious collection housed at NLGRP is kept safe in our vault, which is accessed through an
actual bank vault door. The vault is a separate building specifically designed to safeguard our
collections. The cement walls are more than a foot thick and reinforced with iron rebar. The
vault can withstand tornadoes and floods. Since we are storing a national treasure, security is high.
This cold vault stores the security backup collection for the NPGS. The temperature in
this room is maintained at 0 degrees Fahrenheit or minus 20 degrees Celsius. This is very cold
and our staff follow procedures to ensure they remain safe while working at this low temperature.
Staff wear thick parkas and use the buddy system. We keep track of tray location by
recording the rack number, shelf level, and specific position on the shelf. This location
is recorded in GRIN-Global, associated with each seed packet stored in the tray.
So why do we store seed at such low temperatures? Two factors influence seed longevity and storage:
moisture and temperature. Generally, seeds last longer in cooler and drier conditions than wet,
warm conditions. We dry seeds to an optimal level and then by storing them in cold conditions we can
slow down the metabolic activities that lead to chemical reactions that cause seeds to age. The
cold, dry conditions in our vaults preserve seeds for decades or centuries, depending on
the species. After 10 to 20 years in storage the seed will be checked to ensure it is viable. If
viability is beginning to decline, a fresh sample needs to be sent to us to ensure the accession
is securely backed up with the highest quality seed. Seeds are an amazing adaptation that allow
plant species to persist and spread in diverse environments. Some species such as dates have
proved to have seeds that remain alive for over a thousand years. Other species such as lettuce
have seeds that last only a few years. Wild rice and other species that grow in moist conditions,
including many tropical and subtropical species, have seeds that die when dried.
Although most of the species we care for can be dried and stored in our cold vaults,
we do not take a one-size-fits-all approach when preserving our diverse seed collection.
An important part of the research conducted at NLGRP is discovering new methods for effectively
testing and storing seeds and understanding the processes that influence seed longevity.