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Fort Knox of Genetics

Friday, October 27, 2017
filed under: Research and Development

USDA-Webster’s dictionary defines the term invaluable as: “beyond calculable value, of inestimable worth; priceless.”
       That’s an excellent one-line description for the contents of a three-story building on the campus of Colorado State University in Fort Collins. Inside the building, home to USDA’s National Laboratory for Genetic Resources Preservation (NLGRP), exists a veritable “Fort Knox” of domestically and globally sourced genetics encompassing four main collection units: seed, clonal and microbe germplasm, along with animal semen.
       For the billions of us who must eat to survive, the collections stored at the Fort Collins facility are, indeed, priceless. The lab —initially known as the National Seed Storage Laboratory but later changed to reflect its inclusion of the animal, clonal and microbe collections — serves as the long-term backup for the National Plant Germplasm System (NPGS), which is under the auspices of USDA’s Agricultural Research Service
       Basically serving as USDA’s gene bank, the NPGS dates back more than a century. Along with the NLGRP at Fort Collins (built in 1958), “working” collections are located at various regional genebanks around the country and managed by expert curators. Plant breeders, other scientists and additional “bona fide” users seeking seed samples go through the Germplasm Resources Information Network (GRIN) database to search the collection for their specific needs. (Each sample in the system is catalogued and clearly identified as to its origin, taxonomy and other characteristics.) The appropriate genebank does the actual seed distribution (at no charge). Seeds do not leave the Fort Collins backup collection unless the regional genebank happens to run short of a particular accession.
       The Fort Collins center contains about 560,000 accessions —unique varieties, landraces, genetic stocks and populations of wild species — of the National Plant Germplasm System. In addition, the National Animal Germplasm Program currently maintains about 50,000 unique animals (semen) at the facility. “At our lab, we have about 82% of the total NPGS seed accessions backed up, and approximately 14% of the clonal collections cryopreserved,” says Dr. Stephanie Greene, curator of the base seed collection at NLGRP. The Fort Collins center contains more than a million individual seed samples — 670,000 of which are of NPGS germplasm and another 350,000 that are backup samples for other germplasm preservation institutes, both domestic and international. “When you talk about individual seeds, we have at least three billion,” Greene adds.

Stephanie Greene, seed curator at the National Laboratory for Genetic Resources Preservation, is shown in- side the huge refrigerated vault storing most of the lab’s seed collection.

       Included within the seed unit are 53 species (14 annual, 39 perennial) and subspecies of Helianthus — sunflower — one of the few substantive agricultural crops indigenous to North America. There are just over 5,200 total sunflower accessions in the entire National Plant Germplasm System, with 4,124 of them at Fort Collins. Of those, 4,018 are considered backup samples — i.e., about four-fifths of the entire active collection of sunflower.
       All told, more than 12,000 different plant species are represented within the walls of the NLGRP. While the bulk of the collection consists of seeds related to traditional crops, the lab also includes germplasm (seeds, pollen, plant cuttings) from ornamental and endangered species. Most of the economically significant food, fiber and industrial crops have crop germplasm committees that assist the National Plant Germplasm System in determining priorities for their particular crop — e.g., what needs to be collected and evaluated and where collectors should focus on (both domestically and globally) to find those needed accessions.
       A minority of NLGRP holdings come from other governments and institutes with which the NLGRP has developed collaborative, cooperative relationships. Examples would be the Svalbard Global Seed Vault in Norway, wheat and corn collections from the CIMMYT gene bank in Mexico, and the International Rice Research Institute gene bank in the Philippines. The NLGRP also maintains domestic “blackbox holdings,” such as preserving ash collections for Native American tribes and heirloom varieties for Seed Savers Exchange and Native Seed Search.
       About 20% of the U.S. seed collection is duplicated in the international Svalbard facility at present, with more being added each year.

       What happens with a new seed sample once it arrives at the laboratory in Fort Collins? Following verification of its identifying information with the GRIN system, it’s assigned a serial number, germination card and a bar code label. Seeds are cleaned, if necessary, to remove trash, inert materials, etc. The sample is then placed in an equilibration room set at 5 degrees C (about 41 degrees F) and 25% relative humidity. These parameters allow the seeds to dry slowly, down to a moisture content of between 3-8% (depending on the oil content of the seed). A subsample is then tested for germination percentage and dormancy in order to determine the seeds’ viability.
       “Once the germination tests are completed and we know the viability of the sample, it’s sealed into water-proof packages with a bar-coded label, and we put it in our seed vault,” Greene explains. The seed vault area is actually in a separate building from NLGRP offices and labs, though that separation consists simply of a hallway between the two areas. The vault building “was basically built to be a fortress,” Greene points out. Its thick concrete walls, reinforced with rebar, are meant to protect the treasure trove of seeds from possible natural disasters like tornadoes or flooding. There are extensive safeguards against fire, with backup power systems also in place. The seed storage vault temperature is set at -18 degrees C (0 degrees F).

Christina Walters is research leader for the National Laboratory for Genetic Resources Preservation in Fort Collins, Colo.

       A major change in plant germplasm storage technology at NLGRP, starting about 40 years ago, was the addition of cryopreservation. Located in a large room on the lower level of the NLGRP are dozens of five-foot-diameter steel tanks containing liquid nitrogen at minus (-)196 degrees C (-321 degrees F). Long tubes filled with seeds are held in trays perched within the vapor zone of the liquid nitrogen (which is “only” -175 degrees C).
       Why cryopreservation? In a word, longevity. Seeds stored in liquid nitrogen or its vapor show no metabolic activity, meaning they’ll probably store safely for an even-longer period of time than those in the freezer seed vault — multiple centuries, perhaps.
       Not all seeds are candidates for cryopreservation, however. One reason is simple economics: cryopreservation is expensive, and seeds that survive well in the freezer and are “easy” to regenerate — sunflower and wheat being two examples — can be maintained within NLGRP’s budget using freezer storage. A second reason is that some seeds are truly difficult to preserve, and the lab currently does not have the protocols to do so. Avocado and oak are a couple examples. (Animal semen samples are stored in liquid nitrogen, however, as is the microbe collection and all clonally propagated plants.) At present, about 10% of the NLGRP plant seed collection is under cryopreservation.

       While storage is basic to the NLGRP’s mission, the lab is not just a “bank” where important assets are stored. Substantial research is conducted as well in a variety of areas related to testing and storage protocol. Dr. Christina Walters, research leader at the NLGRP, prefers to use the analogy of a “library” rather than a “bank” when describing the laboratory’s purpose and function. “What we’re actually storing is information — often information that Nature has produced in the form of wild species,” Walters says. “For example, how tolerant is it to drought, or disease, or insects? We can pull out that information — like you would a volume off a library shelf, utilize it, and also associate even more information with it.”
       Among the current research projects being worked on by Walters and her colleagues are: how to collect samples more effectively; how to adequately test them for germination viability without compromising the sample volume; and how to better predict the viable lifespan of seeds in storage.
       “The materials we’re maintaining are for the future,” Walters says. “We need to anticipate the new genes and accompanying information that future breeders will need — and make sure it’s appropriately catalogued so that the inevitable ‘needle’ in the huge ‘haystack’ of our national collection can be found.”

       Sunflower provides an excellent example of why the work of the National Laboratory for Genetic Resources Preservation is so important. As noted earlier, all 53 species and subspecies of Helianthus are represented within the NLGRP collection. The combined genetic diversity represented within all those species remains largely untapped — in good part because of the inherent hurdles of interspecific crossing (hurdles which are gradually being overcome with today’s advanced breeding technologies).
       The sunflower germplasm utilized thus far has allowed for hybridization of this crop and has provided resistance to several major diseases, among other contributions. It has, in short, played a major role in keeping sunflower an economically viable option for farmers. But the evolvement of new disease strains and the ongoing need for additional breeding “tools” (such as genes for drought tolerance and insect resistance) underscore the desirability for continually expanding access to sunflower’s huge pool of wild germplasm.
       Laura Marek and Gerald Seiler are two USDA employees integral to the preservation and analysis of sunflower germplasm. As curator of the “working” sunflower collection at the North Central Regional Plant Introduction Station in Ames, Iowa, Marek’s work is closely integrated with the NLGRP in Fort Collins. She is responsible for the distribution, maintenance, acquisition, documentation and characterization of sunflower germplasm (as well as for the flax, rapeseed, cuphea and other miscellaneous oilseed collections). Marek has participated in numerous Helianthus collection trips and also conducts growouts of accessions at Ames. She is the key contact for sunflower breeders and others seeking specific accessions, ensuring that appropriate accession details are entered into the GRIN database for reviews/requests from researchers both within the United States and abroad.
       Seiler, research botanist with the USDA-ARS Sunflower and Plant Biology Research Unit in Fargo, N.D., has been collecting and studying wild sunflower species for four decades. A longtime member (and chairman) of the NPGS Sunflower Crop Germplasm Committee, he has provided his expertise on a regular basis in guidance to, and support of, curators like Laura Marek at Ames and Stephanie Greene in Fort Collins. Of the 2,300-plus sunflower accessions in the Ames collection, some 1,500 have come from expeditions in which Seiler has participated.
       The work of Seiler, Marek and others underscores the longstanding commitment of USDA-ARS to the preservation of wild sunflower germplasm. It’s a priority now shared by CropTrust, an international non-governmental organization dedicated to the preservation of crop diversity. CropTrust, which operates the Svalbard vault in Norway, “did a global crop wild relative gap analysis and identified that from a global perspective, we really need to secure our Helianthus crop wild relatives,” Greene notes. “Laura and Gerald have been very focused on going out and making those collections.”
       The genetic diversity existing in all those wild relatives is “incredible,” Greene affirms. “With sunflower, there are so many examples of how our genetic resources have been absolutely essential — especially for disease resistance. And, the emerging genomic tools are going to make it easier for us to access that type of diversity.”
         So while it’s a long and winding road leading from those packets of stored sunflower seed in Ames and Fort Collins to the seeds planted by the producer, there’s no doubt the latter would not exist without the former.

– Don Lilleboe