USDA preserving seed and plant diversity for posterity

 By Tim King

The Land Correspondent

Ames, Iowa, The North Central Regional Plant Introduction Station at Iowa State University is one of twenty USDA facilities across the country responsible for conserving seeds and plant genetic resources for posterity. Curators at the Station, often referred to as a seed bank or genebank, care for nearly 52,000 varieties of agricultural, ornamental, and medicinal varieties of plants including mints, amaranths, spinach, parsnips, sunflowers, flax, and legumes. But the heart of the collection is corn which is referred to at the Station by its more widely known name of maize.

“Maize and maize relatives make up about forty per cent of the collection,” Candice Gardener, a Research Leader and self described corn person, said.

Gardner refers to the Ames Station, which was founded in 1948, as an “active genebank site” among the twenty genebanks in the U.S. National Plant Germplasm System.  Active sites are responsible for developing the collection as well as maintaining and distributing the genetic material that they so diligently work to protect. Other sites, known as back-up sites, serve as extra protection for the collections.

“I review requests for germplasm that come in from all over the world,” Vivian Bernau, one of the station’s two maize curators, said. “We distribute it for free for breeding and research purposes. Maize requests are primarily from the U.S. but also come from Europe, Latin America, Asia and South Africa. Most of them come from University researchers but we also get requests from large and small seed companies.”

Vivian Bernau - USDA

The purpose of the Ames Plant Introduction Station, and the national system managed by the USDA and land grant universities, is stated on the organizations logo: “Conserving and Providing Plant Genetic Resources for Agricultural Success”.

USDA has long been interested in seed conservation and distribution.

“Back in the 1890s there was the Division of Seed Industry and that was their purpose,” Candice said. “They distributed seeds to farmers but the problem was that the seeds that they collected couldn’t maintain long term viability. Back then they didn’t have advanced cold storage infrastructure and there wasn’t research on how to store seeds.”

Now days, USDA’s refrigeration and storage system can protect seeds for fifty years and Candice says there is on-going research that may keep them viable for two-hundred years. But Vivian and Mark Millard, the other corn curator at Ames, don’t wait fifty years to grow new seed.

“One of the roles of the curator is to manage the germ plasm of the collection and to monitor the viability of the seed,” Vivian said. “We decide what needs to be regenerated here and we manage some of the regenerations ourselves.”

The maize curators will grow out, and regenerate seed from, about four-hundred varieties on the one-hundred acre farm at Iowa State University at Ames each summer. But maize is global crop and conserving it for the betterment of agriculture requires international collaboration.

“We send material to contractors and collaborators at other locations to capture different environments,” Vivian, who conducted part of her PhD research at the International Maize and Wheat Improvement Center in El Batán Mexico, said. “We send tropical material to Mexico, Puerto Rico, and the U.S. Virgin Islands to regenerate material that can’t be grown in Iowa.” 

Each of the locations outside of Iowa present unique environmental conditions. Puerto Rico, for example has tremendous insect and disease pressure but, at the same time, has many of the right conditions for regenerating tropical maize. Tropical maize, including material held by the genebank,  originates from a variety of environments. One variety, originating from the Andean highlands in tropical South America, created particular challenges for regeneration.

“We have spent years trying to find a good site to regenerate that seed,” Candice said. “Vivian’s experience in Mexico helped us overcome that challenge.”

Laws regulating the international export and import of seeds made regeneration in the Andean nations out of question.

“For the past few years we have been sending Andean maize accessions to a site near the city of Toluca in Mexico for regeneration,” Vivian said. “This location is at 2600 meters (8,500 feet) elevation. Previous attempts to grow Andean maize at locations in Mexico with elevation around 2000 meters were unsuccessful.”

Early efforts to collect maize varieties included looking as far afield as South America but in recent years the focus has been closer to home.

“Right now my focus is on in-bred lines that were developed by public institutions so that those are preserved,” Vivian said. “That is especially important since those public breeding programs are disappearing.”

Each crop collection at the genebank has a committee of experts that advise the curators and help them connect with potential germplasm donations.

 

One of those germplasm lines that are now in the Ames collection is a maize inbred known as B73.

“It’s a variety that was developed in the 70s that became a foundational ancestor for most of the commercial varieties of corn grown in the world,” Candice said. “Vivian’s collection now has four versions of this line and each of those versions have a publicly sequenced genome.”

Vivian explained that every few times a variety is regenerated the genome changes ever so slightly. Those changes are generally not noticeable to the naked eye but, due to advances in genomic sequencing technology, they can be spotted by researchers.

Those subtle changes, and their history, are among the many genetic resources being preserved for posterity at the North Central Regional Plant Introduction Station at Iowa State University in Ames. Information about the U.S. germplasm collections can be found at https://www.ars-grin.gov/Pages/Collections .