Geneva Rootstock

Jul 9, 2024
New Geneva rootstocks to help apple growers with size, yield, disease

New releases from Cornell’s Geneva Apple Rootstock program should benefit growers through increased fire blight resistance, larger-sized and better-yielding fruit and even help growers by supplying sub-dwarfing varieties.

Cornell’s Geneva rootstock program began in 1968 with breeders wanting to develop apple rootstocks that could be dwarfing and fire blight-resistant.
Cornell’s Geneva rootstock program began in 1968 with breeders wanting to develop apple rootstocks that could be dwarfing and fire blight-resistant.

The Geneva 257, Geneva 484 and Geneva 66 rootstocks are licensed through Cornell’s Center for Technology Licensing and follow 40 years of testing. The new rootstocks are touted as offering something for almost every apple grower.

The rootstocks provide additional tools for the apple industry, said Gennaro Fazio, an adjunct associate professor of horticulture in Cornell’s College of Agriculture and Life Sciences (CALS). Fazio and Terence Robinson, CALS professor of horticulture in Cornell’s School of Integrative Plant Science Horticulture Section, work on the rootstocks.

Geneva 257 is a semi-dwarfing rootstock that produces large fruit and high crop load in varieties including SnapDragons and Galas, allowing for more high-density orchards to produce larger fruit.

A characteristic of G.257 is a well-developed root system, one so strong that some nurseries have complained about the difficulty in pulling the rootstocks out of the ground, he said. One of the reasons Cornell released the rootstock was to match it with the weaker growing varieties like Snapdragon, Fazio said.

Another semi-dwarfing rootstock, Geneva 484 is highly productive and yield-efficient. Fazio said G.484 is impressive in its ability to perform well in high-stress environments, including organic growing.

Cornell grad student Todd Holleran, from left, and grad student Davis Upchurch plant Geneva rootstocks.
Cornell grad student Todd Holleran, from left, and grad student Davis Upchurch plant Geneva rootstocks.

A negative is the rootstock produces some, but not many, suckers, shoots or weak branches that grow straight up and require regular removal. The sucker factor is dependent on if the soil is rocky, Fazio said. Still, the small number of G.484’s suckers is smaller than M.7s, he said.

Other benefits should be discovered as more G.484 rootstocks are planted, he said. Fazio said the G.484 was one of the best performing rootstocks in the NC-140 Regional Rootstock Research Project tests.

Geneva 66 is a semi-dwarfing, red-leafed and productive rootstock that is resistant to fire blight.

Fazio said the rootstock has performed well in the NC-140 trials and possesses a favorable and more flexible graft union, a bulge in the trunk a few inches above the soil, as opposed to brittleness issues other rootstocks experienced, he said.

Conell is releasing three rootstocks promoted as offering something for almost every apple grower.
Conell is releasing three rootstocks promoted as offering something for almost every apple grower.

Because of its machine harvesting capabilities, G.66 is likely to gain popularity among cider apple growers. Fazio said the center has performed some tests, but more tests will be necessary.

A handful of groups are breeding cider rootstocks in the U.S. The material they release will be graphed into the Geneva rootstocks to see how well they work. A shortcoming of cider rootstocks, however, is their extreme sensitivity to fire blight, Fazio said.

Climate concerns

The Cornell scientists are also looking into how the changing climate affects apple rootstocks and apple trees in general. They’ve submitted a grant proposal to the USDA.

One reason climate research is important, Fazio said, is because the increased frequency of warming-up periods in January and February that awaken trees that are then struck by sudden cold snaps. The extreme temperature changes destroy parts of the vascular system that are not acclimated to the temperature change, causing intense stress later in the season.

The new rootstocks released by Cornell’s Geneva rootstocks program provides additional tools for the apple industry.
The new rootstocks released by Cornell’s Geneva rootstocks program provides additional tools for the apple industry. Photos courtesy of Gennaro Fazio.

Two other rootstocks are being readied for release. The sub-dwarfing material similar in size to B.9s and M.27s will be designed to fill a hole in the Geneva rootstock portfolio that currently offers vigor categories from dwarf to semi-vigorous rootstocks.

“The hardest thing is long-term field testing. We can use molecular markers, we can use all kinds of new gadgets and methods, but where the rubber meets the road is having them properly tested, for example, by the NC 140 system and similar testing systems around the world,” Fazio said. “Having the data collected in a systematic way, people realize these rootstocks are actually giving, with good statistical confidence, an extra 2 to 3 fruit or 10 fruit per tree, without any negative consequences on fruit production, fruit quality or anything else. And that’s with the bonus of surviving major fire blight events.”

The Geneva program began in 1968 with CALS apple rootstock breeder Jim Cummins and plant pathologist Herb Aldwinkle. Cummins wanted to develop new apple rootstocks that could be dwarfing and also fire blight-resistant. Aldwinkle was instrumental in selection of resistance to root diseases and fire blight. Without those initial crosses, today’s apple industry would look far different.

“Growers needed a place to go for replanting orchards devastated by fire blight and by cold damage, and these Geneva rootstocks have been sort of a salvation,” Robinson said in a news release.

Nearly 70 million trees are planted on Geneva rootstocks around the world. In any given year, U.S. growers plant up to 7 million trees of Geneva rootstocks. Geneva is a registered trademark.

 By Doug Ohlemeier, Assistant Editor 




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