The quest for new apple genes takes ARS plant explorers to Central Asia.
?????? ritz Waller has been in the apple business since the 1960’s. Today he grows 12 popular varieties—including McIntosh, Jonagold, and Empire—on his 250-acre apple orchard in Wolcott, New York, near Lake Ontario. One of his biggest expenses is the chemicals to control insects and diseases. Pesticides cost him about $200 per acre, per year—an expense he’d rather do without
“We get a lot of flak for spraying;” he says. “Farmers would be the first to admit that they would be happier ii they didn’t have to spray.”
Walfer hopes that eventually he’ll be able to grow apples that have genetic resistance to insects and diseases, allowing him to reduce or even eliminate pesticide applications.
The best bet for finding genetic resistance lies in the seeds of the wild apples that Agricultural Research Service scientist Philip L. Forsline and his fellow explorers have found in the mountains of Kazakhstan and Kyrgyzstan.
“I really hope the apples they brought back can help us. Wader says. Forsline is optimistic they will.
In September 1993, he organized and led a collection trip to the two countries in Central Asia. Three other scientists were part of the research team—taxonomist Elizabeth E. Dickson of Cornell University, fruit tree disease expert Gaylord Mink of Washington State University, and breeder Dominique Noiton of Havelock North Research Center in New Zealand. They spent 22 days collecting wild apples in areas where western scientists have never explored before.
Their goal was to scour the rugged foothills for apples in the place where scientists believe the domestic apple (Malus x domestica) was born and evolved—its center of origin, as curators say.
The expedition was a follow-up to an earlier trip that Dickson, Cornell plant pathologist Herb Aldwinckle, and ARS botanist Calvin R. Sperling made to neighboring areas in 1989.
The explorations are part of an ongoing effort by scientists with ARS. universities, and other institutions to preserve valuable genes that may otherwise be lost due to neglect, development, or other factors.
The germplasm—usually cuttings or seeds—is housed in storage facilities where it can be saved for use by breeders to improve agricultural crops.
The need to preserve germplasm is immediate, says Forsline, curator for the apple and grape collection of the ARS Plant Genetic Resources Unit at Geneva. New York. In one area of Kazakhstan, near the capital of Almaty, nearly 80 percent of wild fruit forests have disappeared since I960 because of development. In another area, in Kyrgyzstan, the government has mandated harvesting walnut trees for wood—threatening the diversity of that nut tree.
“We were very fortunate to be able to collect germplasm from these areas, because no one knows how long it will be there,” Forsline says.
It’s too early to tell how valuable the newly collected apple germplasm is. Some of the seeds from the 1993 trip have been planted and have grown into seedlings, but it can take from 5 to 7 years for them to mature and bear fruit. Forsline says 400 trees are now growing outdoors from seed collected during the 1989 trip. But, in their fourth year, only three of them are fruiting.
“We are confident that we collected apples in remote places that western scientists have probably never explored before,” he says. “We think the germplasm will help us widen the genetic base of our collection. Many of the apples we collected arc in the wild species Malus sieversii, a major genetic contributor to M. x domestica.”
In 1989, scientists returned with 114 apple samples—called accessions. During the 1993 trip, they collected 129 more, representing 24 crop species—including apples, pears, hawthorn, hops, walnuts, pistachios, and grapes. They brought back 78 cuttings and 33,000 seeds— including 18,000 apple seeds. Some of the seeds have been planted, have grown into seedlings, and are under evaluation by scientists around the country and world, Forsline says.
Preliminary results are encouraging. Aldwinckle, who chairs the Apple Crop Advisory Committee and is evaluating the germplasm in a cooperative project with ARS, says some of the seedlings from the 1993 trip have resistance to apple scab, based on early greenhouse studies.
Apple scab, a fungal disease, is among the most serious problems for apple growers, blemishing fruit and causing millions in losses each year.
“Resistant seedlings wouldn’t have to be sprayed with fungicides to control the scab,” he says.
Aldwinckle says he will also test seedlings from the 1993 trip for resistance to rust, fire blight, and powdery mildew diseases. He says germplasm he has screened from the 1989 trip has resistance to scab, fire blight, and rust. “We think apple germplasm from the two trips will be of great interest to breeders looking for resistance to these diseases,” he says.”
Wild Apple Antecedents
The 1989 and 1993 trips probably wouldn’t have come about if not for the initial contact between Aldwinckle and Aimak Djangaliev, a professor of Biological Sciences at the Academy of Sciences in Kazakhstan. The 80 year-old Djangaliev has studied the wild apples of Kazakhstan for much of his career and helped arrange the exploration trips. He also came to the United States in 1992 to study apples native to the United States.
Today the United States is one of the world’s leading apple producers. In 1993, U.S. apple production was an estimated 10.7 million pounds. But only 4 of 35 known Malus species are indigenous to the United States, and the 4 are crabapple types that aren’t suitable as eating apples.
Rather, the apples we eat today— Red Delicious, Golden Delicious, McIntosh, for example—and that make up the bulk of U.S. commercial production are fruit immigrants, spread over the last few centuries by people like John Chapman, the legendary “Johnny Appleseed.”
Forsline says that ancient explorers traveled through the Kazakhstan region—nestled between China to the east and Russia to the north—along the silk trade routes. They transported not only silk from the Orient to Europe but also apples. “This is one of the ways that apples are thought to have been spread to other parts of the world,” he says.
But Forsline and other researchers say that the traders who carried the apple seeds probably brought only a narrow genetic sampling with them. That could explain why domestic apples grown today in the United States have a fairly narrow genetic base, making them susceptible to scab and other diseases. The typical eating apple of today probably contains genes from only two or three of the known species, Forsline says. “In apple breeding, we’ve really only scratched the genetic surface, so to speak.”
To broaden the apple’s genetic base, scientists need to bring in new genes from those areas where apples evolved, for it is there they will find the greatest genetic diversity. And the more out of the way and remote the area, the better the chance of finding rare genes that have never been collected before.
Going off the beaten path had its challenges. Many of the remote mountain areas were accessible only by helicopter, hiking, or by taking a jeep down a dusty road for half a day. Sometimes, Forsline says, they were accompanied by aides carrying rifles to guard against a wild bear or boar that might happen to have its eye on the same apple tree.
On a typical day, the scientists collected between 500 and 1,000 apples. Often the apples were small—only about 1 to 2 inches in diameter—because of old age and environmental stresses such as drought and disease. But the fruit were a variety of colors, sizes, and apple shapes—and some, not surprisingly, looked nearly identical to the popular varieties we buy in the local produce section.
“We saw some that looked like Golden Delicious. Red Delicious, and like the New Zealand variety Gala that is becoming popular,” Forsline says. “You can see that the genetic base came from that area,”
Evenings were spent extracting seed from the apples. This usually took place in a yurt, a circular tent made from animal hides and decorated with Persian rugs. The scientists and their hosts would score the apples around their perimeters, just below equator, and twist the two halves apart so they could extract undamaged seeds. Each apple yielded from 2 to 10, depending on its size and other factors.
When it was time for sleep, they slept in bunkhouses that were built years earlier for Khazakh Ministry of Forestry personnel and others exploring the fruit-filled mountains.
Forsline says there was a flurry of activity in the bunkhouses each night, as rodents scampered around, lured by the smell of the extracted seeds.
To increase the apple germplasm collection’s diversity even further, Forsline wants to return to other areas of the region. Perhaps he will go in 1995 or 1996, as part of a 4-year follow-up project on apples with Kazakhstan funded by ARS and USDA’s Foreign Agricultural Service. He says a trip to nearby China would also be helpful, since researchers believe the wild apples there may contain useful genetic material as well.
Meanwhile, apple-grower Warier hopes the potential becomes reality. “This is the future of apples.” he says.
—By Sean Adams, ARS.
Philip L. Forsline is in the USDA-ARS Plant Generics Resources Unit, Cornell University, Geneva, 14456; phone (315) 787-2390, (315) 787-2339.
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