Philip Forsline, PGRU Research Leader

During the 900-day German siege of Leningrad during World War II, the city's food supply dwindled and eventually disappeared. More than half a million Russians starved to death, powerless against the fate imposed by a ruthless war. But some died willingly. In the world's largest seed bank—stocked with hundreds of thousands of plant specimens by the Russian botanist Nikolai Vavilov and his colleagues—many staff members chose to die rather than consume the edible genetic materials they'd been maintaining since the 19th century.

Their sacrifice is an extreme and moving testament to the importance of preserving and protecting plant genetic material, or germplasm. Today, agriculture's success relies on genetic uniformity, which supports large-scale food production. But crops are ultimately weakened by the same homogeneity because it reduces their resistance to disease, pests, and environmental stresses. Genebanks promote the continuation of our food supply by conserving germplasm with valuable genetic traits that can be used to protect and improve commercial crops.

The Agricultural Research Service's (ARS) National Plant Germplasm System (NPGS) includes more than 20 research locations around the United States where scientists safeguard specimens, or accessions, of agricultural crops and conduct research on genetic improvement. Many of these sites—including the Plant Genetic Resources Unit (PGRU) in Geneva, New York—focus on preserving accessions of specialty crops. Some specialty crops make up a significant portion of our diet, so maintaining their genetic diversity is essential. But NPGS researchers don't simply maintain germplasm—they also improve it. And their work has both national and global benefits.

Wild for Tomatoes

Tomatoes are a specialty crop, yet they are among the highest grossing vegetables grown in the U.S. Fresh and processed tomatoes net about $2 billion annually. However, the tomatoes that grace our BLTs and marinara sauces have been thought to possess limited genetic diversity. One method of improving diversity is to breed cultivated tomatoes with wild tomatoes. Unfortunately, the resulting fruit tends to be unpalatable according to molecular biologist Joanne Labate.

Labate, computational biologist Angela Baldo, and geneticist Larry Robertson at PGRU have found greater genetic variety in cultivated tomatoes than was commonly believed to exist. Understanding how to effectively harness this variation could enable breeders to improve the U.S. tomato crop without relying on bitter wild plants.

The PGRU scientists examined publicly available sequence data from the National Center for Biotechnology Information. Using software that Baldo developed with Derek Huntley of Imperial College London, they identified potential small variations in DNA sequences, called "single nucleotide polymorphisms," in 764 tomato genes.

"Of the 53 genes we examined in the lab, 21 revealed significant genetic variations that could be used to aid breeding decisions," said Labate. "In fact, some breeders are already using the information to make genetic maps."

Similar work at PGRU, where scientists maintain more than 5,200 apple trees and 1,400 grapevines in the field, has potential benefits for commercial crops. On trips to central Asia, the probable ancestral home of modern apples, research leader Philip Forsline gathered genetic materials now maintained at PGRU and at the ARS National Center for Genetic Resources Preservation (NCGRP) in Fort Collins, Colorado. Some of those are sources of genetic resistance to common diseases, which breeders may soon be able to use. Nearly 2,500 of the apple field plantings at PGRU are backed up as cryopreserved, or frozen, dormant buds at NCGRP.

Many North American grape species with genes for climate tolerance and disease resistance are also maintained at PGRU. "These grapes can be used in hybridizing to create hardy and disease-resistant grapes for both fruiting grapes and grape rootstocks," said Forsline.

All of this research will eventually improve disease resistance, flavor, and nutrition for some of our most popular crops.