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

ity to latent virusesthan small-fruitedMalus species. Thiswould be especiallyuseful for breedingfire blight-resistantrootstocks. GennaroFazio, directorof PGRU’s applerootstock breedingproject, sees greatpotential—especiallywith crosses betweenKazak applesand elite Americanmaterial. This is thefuture of the appleindustry in anotherfive to seven years.The naturalselection that occursin the CentralAsian forests seemsto have helped theKazak trees developresistance to soilpathogens that canotherwise stuntHerb Aldwinckle, plant pathologist from CornellUniversity, observes a susceptible seedling of M.sieversii inoculated with the bacterium (Erwiniaamylovora) that causes fire blight. (USDA/ARS)young apple orchards and lead to poor growth and lost production.This material is “a treasure trove” of new genetic variants forresistance to Phytophthora cactorum, which causes collar rot, andRhizoctonia solani, an agent of apple replant disease.The progeny of two of the Kazak trees have stood up particularlywell to disease. We put them through what we call “The Gauntlet,”which is exposure in the greenhouse to a series of pathogens thatinclude fire blight and Phytophthora. It usually kills 70 to 80 percentof seedlings. However with this material we got 70 to 80 percent survivalrates. Test of this material by Mark Mazzola of ARS’s Tree FruitResearch Laboratory in Wenatchee, Washington who specializesin soilborne diseases of apples, showed that it is significantly moreresistant to R. solani than the controls he was using. The reductionin root mass due to infection was 30 percent, compared to 70 percentfor the controls. We are considering seeking the inheritance of thisresistance by following it—and the genes causing it—in the progeniesof these plants. This step will take us closer to cloning and isolatinggenes responsible for this resistance.These seedlings have already become part of PGRU’s rootstockbreedingprogram. With the aid of marker-assisted selection, theprogeny from these crosses will become the resistant rootstocks ofthe future. Also, root tissue from the survivors of the Phytophthorainoculation has been used to create a cDNA library that will besequenced as part of an ongoing National Science Foundation ExpressedSequence Tag project. The goal is to find the genes that areexpressed only in resistant individuals.The FutureThe work to further characterize the collection continues butincreased efforts to utilize the germplasm are underway. The goal nowis to release germplasm lines from the collected materials within fiveyears. These collections are now being offered to breeders to developdiverse and useful hybrids for fruit, ornamental, and rootstock value.Today, it is becoming clear that this collection may have an impact ondomestic apples production that will rival that of John Chapman’s.For while Chapman’s iconic work did much to spread apples acrossNorth America, recent findings in the wild apple germplasm fromCentral Asia—Kazakhstan in particular—have genetic resistance todiseases that may help apple breeders breed new varieties that do abetter job of defending themselves against diseases. And the geneticmakeup of the trees may revolutionize the nation’s—and perhaps theworld’s—apple industry.AcknowledgementsA version of this article “Remarkable Kazak Apples” was publishedin the January 2006 issue of Agricultural Research magazine.This research project is part of Plant, Microbial, and Insect GeneticResearch, Genomics, and Genetic Improvement, an ARS NationalProgram (#301) described on the World Wide Web at www.nps.ars.usda.gov.Philip Forsline is the curator of the National Apple Collection and is theresearch leader of the USDA-ARS Plant Genetic Resources Unit, on the campusof Cornell University’s New York State Agricultural Experiment Station locatedin Geneva, NY. Gennaro Fazio is research scientist with the USDA-ARS PlantGenetics Resources Unit located on the Experiment Station Campus. He leadsthe Cornell/USDA apple rootstock breeding and evaluation program. Luis Ponsis a writer with the USDA-Agricultural Research Service Information Staff. HerbAldwinckle is a research professor of plant pathology located at Geneva, NY, wholeads Cornell’s program on fire blight.8 NEW YORK STATE HORTICULTURAL SOCIETY