Califonia Bountiful

Banking on it

Sept./Oct. 2011 California Country magazine

Experts work to protect genetic diversity of world's food supply

John Preece is research leader for the National Clonal Germplasm Repository in Davis, a gene bank created to protect and preserve a collection of fruit and nut crops—about 6,500 plants in all—gathered from throughout the world.

Once a week, John Preece leaves his office and takes a walk through the 74-acre Wolfskill Experimental Orchard. Preece is research leader for the National Clonal Germplasm Repository—a fancy name for a gene bank—in Davis, and the orchard in nearby Winters provides growing grounds for the repository's thousands of trees and vines.

It's just a few miles from Winters, along back roads winding through farmland. The driveway into the orchard is bordered by two long rows of 150-year-old olive trees. Years of sun and wind and weather have worn deep grooves into their trunks and turned them almost white.

Preece parks off to one side, steps out of his car and begins his stroll among rows of fruit and nut trees, grape and kiwifruit vines. He walks past the cherries, sampling fruit when it is in season. Some of the cherries are as tiny as a kernel of corn and the deepest red. Others are plump and brilliant golden orange, blood red or almost black. The clusters of fruit are so heavy the branches bend toward the ground.

The nearby mulberries ripen with the cherries, so he heads there next, picking a few as he goes: white ones, pinkish purple ones, the traditional deep red ones that stain your fingers if you don't handle them carefully. He swings past the walnut orchard, making sure to check on those trees plagued by crown gall, a growth around the base that can kill the tree.

The fruit and leaves represent variation among the collection's plums and mulberries, respectively.

He watches peaches, plums and apricots swell and grow as the season progresses. He inspects the grapevines, carefully moving the leaves aside to take a peek at the growing swags of purple and green fruit. He also keeps an eye on the roses planted alongside the rows: They are indicator plants for powdery mildew, a troublesome fungal disease. Each autumn the leaves in the orchard turn brilliant colors, and winter reveals a myriad of bark patterns and colors.

"It's a living laboratory," Preece said, and it protects and preserves 84 species of stone fruits (peaches, plums, cherries, apricots), 21 species of walnuts, 750 pistachio trees, 3,500 grapevines and 300 figs, as well as almonds, kiwifruit, mulberries, olives, pomegranates and persimmons.

In all, there are about 6,500 plants—accessions, they're called at the gene bank—in the collection. The collection of tree fruit and nut crops comes from all over the world and consists of heirlooms, wild relatives of domesticated crops and some collections from plant breeders such as Luther Burbank, who developed hundreds of varieties of plums and prunes, as well as lilies, the freestone peach, elephant garlic and the Idaho potato.

Preece, who previously worked as a horticulture professor in Illinois for 30 years, has been on the job at the Davis germplasm repository about a year and a half. He leads a team of researchers, scientists and graduate students whose mission is to collect and preserve tree fruit and nut crops, as well as kiwifruit and grapes, from around the world.

He also coordinates plant pathologists, agricultural scientists, plant breeders and others from around the world in their quest to conduct their own research at the orchard. He even manages a clonal propagation program of his own. (Clonal propagation is reproducing plants by cuttings or tissue culture, rather than seeds, so the resulting plants are exactly the same as the parent.)

Plant breeders and researchers use the collection at the gene bank to develop new varieties or to discover more about the genetics of existing ones, Preece explained. He currently has entomologists studying a beetle that causes tiny cankers inside the bark of walnut trees. Another researcher is studying ways to trap the spotted wing fruit fly, a new pest plaguing cherries. Still another is trying to develop walnut rootstock resistant to destructive soil nematodes and the organism that causes crown gall.

But the major use of the collection is by conventional plant breeders who use the genetics of the collection to develop disease- and pest-resistant crops, even ones more suited to dry, Mediterranean-type environments, such as much of California. For example, a fig breeder has used the collection to make some crosses on figs and is monitoring those crosses for taste and hardiness. The grapes in the collection have been used to develop new wine and table grapes.

Preece has had visitors from Turkey, South Korea, Israel, Brazil, Great Britain, Albania, Greece, France, Spain and more. In fact, a recent symposium saw scientists and researchers from 15 countries. Those who cannot make the trip to Northern California can request the repository send them material to study. Some ask for cuttings, seed, pollen or fruit.

"There are no cultivars under patent or proprietary protection," Preece said. "Some of the trees in our collection are wild relatives that may not have any kind of useful fruit on them, but may carry genes that will be useful in the future, so we are part of food safety because we preserve these plants and keep them from going extinct. Sometimes because of human activities, habitat is destroyed, and those plants adapted to a specific region are destroyed. In many cases, we have preserved those crops.

"You never know what that next important plant is going to be, and where those important genes are going to come from, because it depends on the problem that's being addressed. We have new insects and new diseases coming along all the time," Preece explained.

"And interest shifts, too," he said. "Today's fruit du jour is the pomegranate because of its antioxidants. We have pomegranates in our collection with arils (the juice sac with the seed in it, the part we eat) that range in color from yellow to almost white to the deepest red, some soft seeded, some hard seeded. We've had a lot of interest in recent years in our pomegranate collection."

The Davis gene bank is one of three germplasm repositories in the state and one among 22 in the nation.

"We are a cog in the wheel, part of a national germplasm repository system that is run by and paid for by the U.S. Department of Agriculture Agricultural Research Service," he explained.

Each gene bank is entrusted with crops appropriate for the region, and their task is to ensure that crop diversity will be available for future generations. The Davis germplasm repository works closely with the University of California, Davis, Departments of Plant Sciences and of Viticulture and Enology. The Davis gene bank has two sites in the area: one near the UC Davis campus where plants are kept in greenhouses or screen houses in pots, and another as field plantings at the Wolfskill orchard. The property was leased to the germplasm repository to house its collection of trees in 1980. The repository keeps two "copies" of each plant at Wolfskill as a sort of insurance policy in case something happens to one.

"One thing you can say about our collection is the crops are highly nutritious foods. These are the types of foods we should be feeding our children, not junk foods," Preece said. "This collection represents a very important aspect of human nutrition."

Pat Rubin is a reporter in Placer County. She can be reached at

California: Home to three gene banks

The germplasm repository in Davis collects and preserves tree fruit, nuts, grapes and kiwifruit.

The one in Parlier collects drought-tolerant crops and also serves as a growing site for other repositories. For example, researchers are growing several types of wheat for the Aberdeen, Idaho, repository and garlic for the Pullman, Wash., repository. California's mild climate allows researchers to grow several crops a year of some plants, helping replenish germplasm supplies for repositories in colder climates.

The germplasm repository in Riverside collects citrus and dates.

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