The Apple Collection in Geneva, NY - New York State Horticultural ...

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A grafted tree produced in Geneva, New York,from a scion taken from a tree in a Kazakh appleforest. William Srmack, farm manager at Geneva,displays the quality fruit of this genotype that haspotential use by breeders. (USDA/ARS)Phil Forsline and Herb Aldwinckle evaluating applevarieties from Kazakstan. (Helene Bozzy, SEPPIA)Technician Greg Noden characterizes morphologicaltraits of M. sieversii fruit and cuts the fruitin preparation for taking a digital image for thewebsite www.ars-grin.gov/gen (USDA/ARS)the Genetic Resources of Grapes, Apples, and Tart Cherries.” Intotal, 6,883 diverse apple varieties are maintained at the PGRU.This includes 2510 apple clones (1,410 Malus x domestica; 329Malus hybrids; and 771 clones belonging to ~54 Malus species)all maintained in duplicate field plantings at Geneva. Additionally,1,565 seed lots of wild Malus species including approximately950 seed lots of Malus sieversii, the main progenitor species of thecultivated apple (M. x domestica) from Central Asia are kept incold storage at the PGRU with back ups at the USDA-ARS NationalCenter for Genetic Resources Preservation (NCGRP) in Ft. CollinsCO. About 2,808 seedlings representing 310 of these M. sieversiiseed lots are being grown as trees for field evaluation. Of the 6,883apple varieties, a core collection of 255 clones has been designed torepresent the diversity of apple. Furthermore, approximately 2,275clones are backed up in cryogenic storage (liquid Nitrogen) at theNCGRP and 436 are also in cryogenic storage on-site at PGRU.Most of the varieties used as parents for breeding new varietiesof apples in the U.S. come from what is known as the “North Americagene pool.” It dates back to seedling orchards planted when settlersfirst arrived here between the 17th and 19th centuries. This source isoften referred to as the “Johnny Appleseed gene pool.” This alludes toJohn Chapman, who during America’s infancy spent nearly 50 yearsplanting apple seeds throughout the wilderness of Pennsylvania,Ohio, Indiana, and Illinois. Many common varieties—includingRed Delicious, Golden Delicious, Jonathan, and McIntosh—werediscovered as chance seedlings from this pool. Apple breeders havemade great strides already using them to produce new ones that arenow in the world marketplace. But the fact is that this gene pool isvery narrow compared to what can be found by tracing further back,through Western Europe, to Central Asia where it is thought applesoriginated. Indeed, the mother lode of apple genes is in Central Asia—Kazakhstan and Kyrgyzstan in particular—which is likely the centerof origin or ancestral home of familiar domestic apples (Malus xdomestica) such as Red Delicious, Golden Delicious, and McIntosh.Widening a Narrow Base—Collection Expeditions toCentral Asia, the Apple’s Ancestral HomeSilk Road traders and their predecessors started the spread ofapples from Central Asia to other parts of the world. But the seedsthey carried likely represented a narrow genetic sampling. That’sprobably why today’s American domestic apples have a fairly narrowgenetic base that makes them susceptible to many diseases.From 1989 to 1996, the USDA sponsored expeditions to CentralAsia to collect seeds and tree samples (scions) from unique applestrees growing in natural forests. Seven expeditions were completedfrom 1989 to 1999. Four of them were to Central Asia to collect thewild apple Malus sieversii, the main progenitor of the commercialapple, M. x domestica.The Experiment Station’s Herb Aldwinckle was a participanton the first trip to Central Asia in 1989. Philip Forsline, who is thecurator of the national apple collection, was a member of seven ofthe trips, including four to central Asia to collect apple material,conserve it, and, after evaluation, distribute it to breeders and geneticistsworldwide. Other trips were to China (Sichuan), Russian,and Turkish sectors of the Caucasus region, and Germany. He recallsthe expeditions as hard work. Herb joined Phil also on the trips toChina and Turkey. Often, the only way of getting to remote mountainareas was by helicopter, long hikes, or half-day-long jeep rides downbumpy, dusty roads. What we collected made possible our re-creationof Kazakhstan, China and the Caucasus region here in Geneva. Allthat effort is now bearing fruit, literally and scientifically. We tappedmillions of years of adaptations to improve today’s apple.The trips resulted in at least a doubling of the known geneticdiversity of apples. In all, the scientists returned from Central Asiawith 949 apple tree accessions. Most of the specimens were broughthere as seed, but 50 were cataloged as “elite clones”—grafts of theoriginal trees. The seeds gathered on the trips increased PGRU’sapple collection by 1,140 samples, to over 3,900. The visits to Kazakhstanand Kyrgyzstan alone added 949 accessions of M. sieversii.6 NEW YORK STATE HORTICULTURAL SOCIETY
Technician Todd Holleran waters young apple rootstock seedlings that havesurvived the “gauntlet” of disease screens. These disease-resistant seedlingsare derived from a cross between resistant wild M. sieversii selections andelite apple rootstocks from the Geneva breeding program. (USDA/ARS)Wild apples from Kazakstan that have “almost” commercial quality. (HeleneBozzy, SEPPIA)Unfortunately many of these natural forests sites are threatenedby over grazing, and insidious human practices (clearing areas foragriculture or construction, grafting forests trees to domesticatedvarieties).Remarkable Kazak ApplesAmong all this material, it is the Kazak samples that have becomethe apple of Forsline’s eye, so to speak. It turns out that thisgene pool is much more diverse than we had originally thought.Especially noteworthy are accessions collected there of M. sieversii,an important forerunner of the domestic apple. Although many ofthe Kazak apples lack the size and flavor needed for commercialsuccess, it’s the trees’ ability to resist diseases that sets them apart.Breeders will be able to cross them with palatable varieties to develophigh quality commercial varieties.Success Against Plant DiseasesForsline and Herb Aldwinckle from Cornell University alongwith colleagues from PGRU, and other institutions have been characterizingthe trees’ germplasm for the last decade. Germplasm refersto the genetic material that carries the inherited characteristicsof an organism. The Kazak trees have shown significant resistanceto apple scab, the most important fungal disease of apples, whoseoutbreaks blemish fruit and defoliate trees. Twenty-seven percent ofthe Kazak accessions were resistant to it. This makes sense becausethe tree co-evolved with the disease through natural selection.In addition, samples from species collected at other expeditionsites have provided promising news in the fight against fire blight.Fire blight destroys apples, pears, and woody ornamentals in theRosaceae family. Herb Aldwinckle reports that seedlings fromdifferent populations of M. orientalis from the Russian Caucasusand Sichuan regions effectively resisted the disease, with Russianaccessions scoring 50 to 93 percent resistance. Other researchershave found genes in these apples that allow them to adapt tomountainous, near-desert, and cold and dry regions.In an early effort to utilize the natural disease resistance of theKazak trees, Forsline led a project which involved scientists fromCornell and the University of Minnesota, as well as collaboratorsfrom New Zealand and South Africa, in which the popular Galaapple variety was crossbred with seven Kazak accessions. Thisproduced seven populations of 200 seedlings each. In one of thesepopulations, we achieved a 67 percent resistance rate against applescab. This may be the source of a more durable, scab-resistantapple. Also, about 30 percent of samples inoculated with fire blightresisted that disease.Rootstocks, TooThe fire blight resistance of the Kazak M. sieversii and the RussianM. orientalis may convey resistance to fire blight and less sensitiv-Members of the American Nationalfamily of companiesNEW YORK FRUIT QUARTERLY . VOLUME 16 . NUMBER 1 . SPRING 2008 7
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