The USDA/Cornell Apple Rootstock
Breeding and Evaluation Program

The USDA-ARS / Cornell University apple rootstock breeding project was initiated in 1968 as a Cornell project. The original objective was to develop rootstock genotypes with improved nursery and orchard characteristics that are better adapted to the abiotic stresses of New York and surrounding areas. As interest grew in high density planting systems beginning in the 1970s, the focus was modified to include the biotic stresses. Resistance to the crown rot and fire blight pathogens, both exacerbated by the weaker root systems and higher plant densities of the more profitable and productive dwarfed tree plantings, became a major goal of the breeding program.

Improved productivity and precocity, combined with resistance to critical diseases and tree size control, remained the goals of the project through the tenure of the principal investigator, Dr. Jim Cummins, who retired in 1993. The project was maintained at a reduced level by Dave Gill from 1994 until he retired in 1997. Drs. Terence Robinson, Herb Aldwinckle, and Hugh Price, faculty members at NYSAES, have also contributed their expertise in horticulture, pathology, and administration, respectively, throughout the transition period, and remain key collaborators in the project.

During the 1990s, four promising genotypes were released from the program, capturing the attention of the domestic apple industry. In 1998 the apple rootstock breeding program was resumed through a cooperative agreement between Cornell University and the USDA, with the addition of a rootstock evaluation component. Dr. Bill Johnson now leads the program with a mandate to breed rootstock cultivars to meet the needs of the US apple industry and to evaluate new rootstock genotypes from foreign breeding programs.

Rootstock cultivars require extensive evaluation through stoolbed trials, biotic and abiotic stress screenings, and multiple orchard performance tests. Rootstock breeding programs are only operated by public agencies due to the long development period (25 to 30 years minimum) required to evaluate ultimate tree size and productivity in each breeding cycle, a time scale that precludes commercial breeding projects.

The USDA-ARS / Cornell University apple rootstock program is unique for the focus on disease resistance and orchard performance. The program has drawn heavily upon the genetic resources of the newly acquired apple germplasm at the Plant Genetic Resources Unit in Geneva, and has screened over 700 accessions of wild and cultivated Malus spp as potential parents. More than 100 genotypes have been used as parents in the breeding program, providing a broad genetic base for potential future cultivars.

Currently all seedlings are subjected to rigorous screening programs to eliminate disease susceptible individuals prior to planting in the field. Rootstock genotypes are selected on the basis of abiotic stress tolerance, disease resistance, productivity, and precocity in orchard tests. This breeding protocol contrasts sharply with those of other breeding programs, which have concentrated effort on improving the stoolbed and nursery performance of rootstock cultivars and have employed the much narrower range of traditional rootstock genotypes as parents of breeding populations. As a result, the USDA-ARS / Cornell University rootstock breeding program is recognized worldwide as the most promising source of new, disease resistant and productive rootstock genotypes for the future.

Because of the extensive and ambitious scope of the USDA-ARS / Cornell University rootstock breeding program, and because of past problems with mis-identified rootstock genotypes released from the program, there is concern about the record-keeping in the project. The current focus of the program is to verify the correct identity of elite selections from the program, to implement a modern record-keeping system, and to improve the transparency of the program so that the clients (nursery operators and apple producers) have a clear understanding of program operations and easy access to the information available for elite rootstock genotypes.

Through the USDA-ARS / Cornell University cooperative agreement the resources were mobilized for continued operation of the rootstock breeding and evaluation program. The agreement broadens the scope of the program from a focus on regional concerns to address the production constraints of all the US apple production regions. In the future, the breeding program will continue to develop precocious and productive disease resistant rootstock varieties with a range of vigor from fully dwarfing to near standard size. In addition, there will be a renewed emphasis on nursery propagability, lodging resistance, tolerance to extreme temperatures, resistance to the soil pathogens of the sub-temperate regions of the US, and tolerance to apple replant disorder.

Rootstock Breeding & Evaluation Page
Horticultural Sciences Faculty Page
NYSAES Home Page

Page maintained by wcj4@cornell.edu
Last modified August 20, 1999
http://www.nysaes.cornell.edu/hort/faculty/johnson/overview.html