History and New Releases from the Geneva® Apple Rootstock Breeding Program

Authors: Fazio, Gennaro; ROBINSON, TERENCE - Cornell University

Submitted to: Acta horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: The article describes the history of the Geneva® apple rootstock breeding program, its initial goals and the unique traits it has discovered that are well beyond what was imagined at inception. As every piece of orchard land is different (type of soil, climate, water resources, infrastructure, and apple variety) so are the rootstock solutions that have been developed by the breeding program, uniquely designed to match some of those situations. The latest three releases from the breeding program, Geneva® 257 (G.257), Geneva® (G.484), and Geneva® (G.66) address needs from organic apple growers, small fruited apple varieties and difficult replant disease conditions.

Technical Abstract: The Geneva® apple rootstock breeding program has been operating at Cornell University since the late 1960s with the main goal to develop new material resistant to pests and diseases endemic to North America. The U.S. Department of Agriculture joined this effort in the late 1990s leveraging field, laboratory, technical and germplasm resources the program had and adding a major component on genetics, genomics and marker assisted breeding. The project has maintained the focus on resistance to fire blight, crown and root rot while evaluating material for increases in orchard productivity. The program also worked with external national and international institutions such as the NC-140 rootstock evaluation collaborative group to test its products in multiple environments. The process, which for some apple rootstocks has spanned 3-4 decades from initial cross to final release, has produced several rootstocks including G.11, G.16, G.41, G.935, G.214, G.814, G.778, G.222, G.213, G.210, G.969, G.890. Each of these rootstocks has displayed outstanding properties as well as some shortcomings. While breeding, the program made discoveries about the nature of dwarfing, early bearing and the propensity of the rootstock to impact partitioning of photosynthate away from excessive vegetative growth and into fruit production. More recently, the program has made discoveries on additional traits that modulate fruit quality (fruit size and nutrient content), tree architecture, influence on chilling hour requirement, graft union strength, brittle or malformed graft unions, root morphology and metabolic compounds, phytohormone influence on grafted scions, interaction with woolly apple aphids, interaction of rootstocks with multi-leader training systems, and interaction with soil properties (pH and composition). As we learned more about each of the Geneva® rootstocks, it has become clear that the observed diversity in traits is an asset to the diverse applications/environments representing apple orchards worldwide. Each orchard is unique in its soil and climate characteristics, this combined with different scion cultivar characteristics and vigor means that no one rootstock is the best choice in all situations. This awareness leads the program to continue to pursue new rootstocks which are better in certain niche situations than all other rootstocks. All these considerations, in addition to new nursery and field performance results have led the Geneva® apple rootstock breeding program to release three new rootstocks: Geneva® 257 (G.257), Geneva® (G.484), and Geneva® (G.66).