When the Russian wheat aphid spread to the United States in 1986, just about all of the country’s commercial wheat varieties were susceptible to it.
To find resistance to this insect—which would end up costing American wheat and barley farmers billions of dollars in losses—Agricultural Research Service (ARS) scientists turned to the ARS National Small Grains Collection in Aberdeen, Idaho. They screened more than 30,000 wheat and 24,000 barley samples, or “accessions,” for resistance.
ARS researchers identified more than 300 resistant wheat germplasm accessions and 40 promising barley lines as potential sources of resistance genes, mostly from that ARS germplasm collection.
From this germplasm, breeders began a crash program to develop new varieties, and the crisis was haulted.
The Aberdeen grain collection is one of several working plant collections that make up ARS’s National Plant Germplasm System (NPGS). Each collection concentrates on specific types of plants. The National Center for Genetic Resources Preservation (NCGRP) in Fort Collins, Colorado, is where plant germplasm is kept in long-term cryogenic storage. The NPGS is the nation’s storehouse for preserving thousands of agronomically important plants and their relatives.
“The National Plant Germplasm System is also our stockroom for tools to deal with problems like a pathogen mutating or when a new pest makes it into the United States,” says David Ellis, a curator and plant physiologist at NCGRP.
“Then, researchers from all over turn to our germplasm collections to find the building blocks—the genes they need to breed a solution to the new problem.
“You never know what problem we will have to face at any time. The staggering increase in global commerce alone means more spread of diseases, weeds, and pests. Having a resource like the germplasm collections already in place is our security that we will be able to react quickly when we are confronted with a new problem,” says Ellis.
Germplasm collection and preservation are not actions that can wait until new genes are needed. Global climate change, loss of habitats, the spread of monoculture cropping, and even war and political instability threaten genetic variation in agriculture and in the wild. Pathogens and pests continue to evolve. So protecting as wide an array of crop varieties and their wild relatives as possible is the best insurance policy for the present and for the future. It is impossible to tell ahead of time just what genes a plant may offer that may one day be needed.
There is, for example, the scraggly wheat that USDA plant explorer Jack R. Harlan and his Turkish colleague Osman Tosun collected from a field in Fakiyan Semdinli, Turkey, in 1948. At the time the sample was taken, the wheat looked terrible—it lodged, had no winter hardiness, and was susceptible to leaf rust. By itself, “it was a hopelessly useless wheat but was dutifully conserved,” Harlan wrote of the wheat that was placed in the National Small Grains Collection simply as plant introduction (PI) number 178383.
But 15 years later, when U.S. wheat breeders were looking for a way to breed resistance to a new stripe rust outbreak, PI 178383 was found to have resistance to 4 races of stripe rust, 35 races of common bunt, and 10 races of dwarf bunt—as well as tolerance to flag smut and snow mold. Today, PI 178383 appears in the pedigree of virtually all wheat grown in the Pacific Northwest.
Breeders turn to the germplasm collections not just to solve disease and pest problems, but also to expand drought and temperature tolerance, adapt plants to new growing conditions, and make them more productive, nutritious, durable, or simply better tasting.
Nor does ARS maintain its germplasm collections just for the United States’s agricultural security and progress.
“The NPGS distributed more than 172,000 plant samples worldwide in 2007,” says Ellis. “They went to breeders and researchers and will contribute to development of crops we will need or want. Genetic resources like those from ARS’s National Plant Germplasm System are simply the foundation of our agricultural future.”—By J. Kim Kaplan, Agricultural Research Service Information Staff.
The National Plant Germplasm System plays a role in many of ARS’s national research programs, described on the World Wide Web at www.nps.ars.usda.gov.
David Ellis is with the USDA-ARS National Center for Genetic Resources Preservation, 1111 S. Mason St., Fort Collins, CO 80523-4500; phone (970) 495-3227, fax (970) 221-1427.
Safeguarding Our Crops
In Griffin, Georgia, the Agricultural Research Service houses the Plant Genetic Resources Conservation Research Unit, led by Gary Pederson. The unit, part of the National Plant Germplasm System (NPGS), is a gold mine of plant species with more than 88,000 plant accessions in stock. It also serves as an invaluable resource for researchers who are developing new cultivars for farmers facing tough growing conditions. More than 30,000 free samples are sent out each year.
Alterations in climate, insect pests, and water supply, among other factors, affect viability and profitability of crops. But ARS safeguards the continued abundance of crops by taking a long-range view of crop production. Scientists at Griffin and other ARS locations are the keepers of plant germplasm. They are tasked with safeguarding samples of all crops of agricultural importance in the southeastern United States and providing seed stock to researchers and educators anywhere in the world.
Trips are also conducted to find new varieties to add to the collection. For instance, watermelon accessions previously collected from Egypt, India, Iran, Serbia, and Zambia were reported in 2007 that have resistance to broad mite. This pest is not currently found in the United States, but it could become a problem in the future.
Even samples collected decades ago may be sources of disease resistance. One such peanut accession, known as PI 203396, was collected in a Brazilian market in 1952 and is currently the source of resistance to tomato spotted wilt virus (TSWV) in most of the peanut cultivars grown in the southeastern United States. TSWV is a major peanut disease.
The unit boasts one of the most varied collections of any ARS laboratory in the NPGS. It includes peanuts, legumes, sweetpotatoes, peppers, squash, annual clover, eggplant, and sorghum, to name a few.—By Sharon Durham, Agricultural Research Service Information Staff.
"Germplasm: Insurance for the Future That Pays Current Dividends" was published in the May/June 2009 issue of Agricultural Research magazine.