November 15, 2001

Scientists Work to Preserve Apple Diversity

Print More

If you ask Phil Forsline what his favorite apple is, he’ll tell you he has four.

“It all depends on what mood I’m in,” he says.

When he wants pure apple flavor, he grabs a Jonagold. For most occasions, though, he’ll reach for an Empire — which he can usually eat two at a time because they’re “satisfying, but not satiating.”

When he wants to sit around in the evening and crunch for a while, he likes the Mutsu, also called Crispin.

“It’s a big apple.”

And finally, when the winter months are dragging on, and all the other apples are getting old, he chooses Fuji.

Forsline should know. He is a horticulturist for the USDA Agriculture Research Service and curator of the apple and sour cherry collections of the Plant Genetic Resources Unit (PGRU) at Cornell’s Geneva Campus. In charge of its 2,500 different apple varieties which are planted on 50 acres of land, he’s tasted the fruit of every one.

But Forsline said he is concerned by losses of genetic diversity in commercial apple varieties. Today’s most common grocery store varieties — Gala, Jonagold, Fuji, Red and Golden Delicious and others — can trace their ancestry back to only a few parents, and that is a problem, according to Forsline.

“It’s a challenge to grow [apples]. They require a lot of pesticides to give good [fruit],” he said.

“The problems start in orchards with disease and pests and then continues into storage. Apples have a shallow gene pool that just doesn’t have the depth to combat these problems,” said Jim Luby, Professor of Pomology and Plant Breeding at the University of Minnesota, who has collaborated with Forsline on a number of projects.

Apple trees must be reproduced through grafting, an asexual process, to maintain their favorable characteristics. However, their pathogens and pests are under no such constraint, and readily swap genes through sexual recombination. This results in more and more well-adapted pests, and apple trees that are increasingly vulnerable, according to Forsline and his colleagues.

As a result, unsprayed apples are rarely blemish-free and are frequently riddled with the signs of insect, fungal, and bacterial guests. The only way to produce the picture perfect apples found in the grocery store is through the extensive use of pesticides.

“I never plant eating apples in my yard,” says Forsline, “because I don’t want pesticides around the house.”

But Forsline and other scientists at Geneva are working to help alleviate these problems with the help of trees which, unlike domestic trees, have not had their genes subject to selection by human cultivation for 6,000 years. Presumably, these trees preserve all of the apples’ genetic diversity. They are found in the apple’s homeland — the Tien Shan mountains of Kazakhstan — to which these scientists went.

The “All-Central Asian” Fruit

It had been known since the early 20th Century that Kazakhstan was the likely source of the main genetic constituent of our domestic apple, the wild Malus sieversii. The dissolution of the Soviet Union in 1989 afforded American scientists their first opportunity to investigate the apples found there, according to Herb Aldwinckle, a scientist in the Plant Pathology Department at Geneva, and one of the first to visit Kazakhstan in that year.

“It was hard to get the authorities to agree to let us collect there.

frustrations were the biggest problem,” said Aldwinckle.

Aldwinckle, Forsline, Luby and others have traveled around Kazakhstan by helicopter (and in later trips by bus — the authorities claimed there was no fuel for the helicopters) collecting cuttings and seeds to take back to the United States. There have been four such trips since the area was opened to U.S. scientists in 1989.

Apples grow wild in the forests of Kazakhstan. In his book, The Botany of Desire, apple expert Michael Pollan describes how the Silk Road passed through this region, and travelers likely carried apples with them westward, spreading them into the mideast, the Roman Empire, and Europe. These trees in turn hybridized with other apple species found along the way, were cultivated by Romans and others, and gradually assumed their modern form.

Because the apple is native to Eurasia and not North America, Forsline has suggested that the “… quintessential ‘All-American’ fruit should more aptly be called the ‘All-Central Asian’ fruit.”

Immigrants to the United States brought cuttings of European varieties with them, but these were usually maladapted to the harsher North American climate, and rapidly died. Only trees planted from seed, called “pippins”, could survive. The fruits of these trees were by and large ‘spitters’ (apples too sour or bitter to be consumed). They were good only for cider — a hard drink by nature in those days, since refrigeration was a century or so away. However, chance seedling would occasionally produce fruit that was tasty enough to eat. And thus originated McIntosh and Delicious, Northern Spy and Newtown Pippin, and a whole host of apples uniquely adapted to the American environment, according to Pollan’s book.

Over time, however, popular taste has narrowed the array of apple trees commercially grown to the descendants of only a few varieties: Jonathan, McIntosh, Golden Delicious, Red Delicious, and Cox’s Orange Pippin.

“Ninety percent of the apples grown in the world have six parents, and two of those are the parents of the others,” said Luby.

Further, apples can only be propagated by cuttings if their favorable characteristics are to be preserved and not lost to genetic recombination in the next generation. This is called grafting, and it involves taking a cutting from the desired fruiting tree and splicing it with a hardy rootstock. Now, after generations of this practice and the decrease in the number of grown varieties, commercial apples’ genetic diversity has dwindled, leaving them open to the predations of insects and pathogens.

But in Kazakhstan, none of this has taken place. Apples as small as grapes and as large as familiar eating apples are found there in a wide range of colors and flavors, though by and large they are ‘spitters’. Many of these trees show strong resistance to disease, cold hardiness, favorable growth patterns or promising rootstock characteristics, according to Forsline.

“Some of the Kazakhstan apples are very close to commercial quality [in terms of fruit],” as well, Luby added.

In the course of their travels, the scientists have run into their share of mishaps. “On a bus ride in ’95 the bus broke down in the desert for seven hours. I thought maybe it was more fortunate we had the bus instead of the helicopter — I’d rather have the bus break down,” remarked Forsline.

On another occasion, Aldwinckle and Forsline were together in China when they came upon a troupe of monkeys. “We thought they were cute until they attacked us [for our apples],” remembered Aldwinckle. How did they get out of that situation? “We let them have the apples.”

And finally, Luby recalls the great hospitality of their hosts.

“One of the traditions they have is to give very long toasts with vodka. Everyone is expected to give a toast over the course of the evening, and when they’re done, bottoms up,” Luby recounted. With 15 to 20 guests at each dinner, this added up.

“[Forsline] and I figured out how to get water into our glasses because we could not possibly keep up. But one night we came over and all the water had been colored red.”

Seeds, pollen, cuttings, or other materials brought to
Cornell are stored and documented at PGRU to become part of a genetic repository. Preserved material can then be distributed to researchers or breeders for their work in improving the apple, according to Forsline.

Aldwinckle has been able to screen many of these trees for resistance to apple scab, fire blight, and cedar-apple rust, diseases that cause severe losses among cultivated apples.

“We’ve been evaluating this material for resistance to diseases for a number of years. We’ve found resistance in nearly every batch of seed we’ve brought back from Kazakhstan,” said Aldwinckle.

Even more promisingly, the resistance seems to stem from many different genes.

“That’s good because we can’t rely on just one,” he added.

All told, they’ve collected around 130,000 seeds from 900 sources, and 15 – 20,000 of these have been planted at Geneva or elsewhere.

The reason for their collecting, screening, documenting, and distributing of these trees is to incorporate some of their genes into commercial varieties. This could occur through conventional breeding or genetic engineering, according to Aldwinckle.

“We’ll start making crosses next year [since] our trees started having flowers this year,” said Luby, whose program is involved in breeding for disease resistance and cold hardiness.

“Preserving these apples allows us to preserve all the genes so that when new problems crop up in the future, we’ll have solutions ready. These collections provide great insurance for the future — against diseases, insects, and even global warming,” Aldwinckle said.

During their trips, Aldwinckle and Forsline were disturbed by the extent to which they had observed development already endangering the trees in Kazakhstan. This added to there motivation.

“We’d like to see that the diversity of the apple is preserved for future generations,” Aldwinckle said.

Forsline will give seeds of the Kazakhstan apples to anyone willing to grow them on their own land and report back to him on the results. According to him, to date he has received 20 requests and distributed about 100 seeds in this manner.

Archived article by Jennifer Frazer