STAGE 3
Initial test orchard establishment, precocity evaluation and selection are carried out in years 7-9
(100 rootstock genotypes).Three finished trees on each rootstock genotype are planted in an
initial test orchard.In addition to the test genotypes, size standard rootstock varieties are
included (M.27, M.9, M.26, MM.106, MM.111).Trees are trained to develop an open branching
pattern, but pruning is minimized to allow an accurate assessment of size control.Data are
collected annually for yield, yield efficiency, suckering, anchorage, timing of bud break, and
response to any unique stress events.

In April we planted an initial test orchard with 174 new rootstock genotypes. Trunk cross-
sectional area, suckering, yield, and fruit size data were collected on all initial test orchard trees
planted in 1996. Fruit number data were collected in the 1997 planted orchard on highly
precocious rootstocks.

STAGE 4
Initial test orchard evaluation and selection and elite stoolbed establishment occur in years 10-12
(50 rootstock genotypes).Promising rootstock genotypes are stooled during year 10.Elite
stoolbeds of 1-3 m (3 to 10 feet) are established in year 11 using liners or, if necessary, root
cuttings from orchard trees.In year 12, liners of rootstock genotypes that continue to perform
well in initial test orchards are collected.The most promising genotypes evaluated from other
breeding programs may join the evaluation portion of the Cornell/USDA program as stage 4
genotypes if they have not yet been commercially successful internationally.

Trunk cross-sectional area, suckering, yield, and fruit size data were collected on all initial test
orchard trees planted in 1992-1995. A large new intermediate stage testing stoolbed was layered
to begin medium-scale liner production of promising rootstock genotypes for testing beginning in
1999.

STAGE 5
Liner production, stoolbed evaluation and nursery tree growth occur in years 13-15 (25 rootstock
genotypes).Liners in the nursery are budded with a minimum of 2 commercially attractive scion
cultivars, with a goal of producing 30 finished trees.Initial test orchards are removed after
harvest in year 15 (after 9th leaf).Liners are also collected from elite stoolbeds and subjected to
evaluations of disease resistance and stress tolerance (extreme temperature soil tests, replant soil
tests, fire blight tests, crown rot tests, latent virus tests, anchorage tests, graft union strength
tests).

Biotic and abiotic stress tolerance tests for intermediate stage rootstocks are planned for 1999.
Tests for fire blight tolerance, midwinter chilling injury, and high soil temperature stress are
planned for 1999. Fifteen intermediate and advanced stage selections were budded in 1998 with
3 latent virus-infected genotypes to characterize their reactions during nursery growth.

STAGE 6
Intermediate stage orchard establishment and early evaluation occur in years 16-18 (10 rootstock
genotypes).Intermediate stage orchards are planted beginning in year 16 in New York and
Washington environments.Each orchard includes 3 commercial standard genotypes (M.9, M.26,
MM.106) and approximately 10 elite rootstock genotypes that have shown promise in elite
stoolbed liner production, initial test orchard performance, and biotic and abiotic stress resistance
screens.Orchard trees are evaluated for precocity in years 17-18.

No new intermediate stage orchard trials were established in 1998. In 1999 we established a
central Washington (WSU Tree Fruit Research and Extension Center, Wenatchee) intermediate
stage test with 10 new rootstock genotypes, 10 single tree replications per rootstock, and Malling
series standard check varieties. Trunk cross-sectional area, suckering, yield, and fruit size data
were collected on all existing intermediate stage test orchard trees in New York.

STAGE 7
Intermediate stage orchard evaluation and commercial stoolbed trials occur in years 19-21
(5 rootstock genotypes).Intermediate stage orchard trial data collection continues.Biotic and
abiotic stress screenings of rootstock liner trees are completed.The most promising rootstock
genotypes (a maximum of 5 per year) from the Cornell/USDA program are distributed to
cooperating nurseries for commercial stoolbed trials beginning in year 19.Liners are collected
from stoolbed trials and budded to produce finished trees for NC-140 and/or on-farm trials.
Most promising Geneva rootstock genotypes are submitted for pathogen-free status certification
(NRSP5, Prosser, WA) to enable international distribution.

We will be implementing the new commercial stoolbed trial procedure beginning in 1999 by
distributing 5 promising rootstock clones to 2 cooperating commercial nurseries (TRECO in
Oregon and Willow Drive in Washington). In 1999 the rootstocks distributed for stoolbed trials
will be CG.935, CG.041, CG.179, CG.707, and CG.210. Rootstock selections from foreign
programs will be included in stress screenings as material is available.

STAGE 8
NC-140 and on-farm trials and distribution to all cooperators occur in years 22-24 (1-2 rootstock
genotypes).Intermediate stage orchard trial data collection continues.For outstanding rootstock
genotypes from the intermediate stage orchard trials and commercial nursery stoolbed trials, liner
production from cooperating nurseries is used to propagate trees for NC-140 and/or on-farm
trials.NC-140 trials and on-farm trials are established.Best rootstock genotypes are distributed
to domestic cooperating nurseries for propagation and to international cooperating nurseries and
institutions for propagation and local evaluation trials.Rootstock genotypes that are
commercially successful internationally join the evaluation program as stage 8 materials
following biotic and abiotic stress screenings.

Recommendations for rootstock selections to include in NC-140 plantings will be made based on
intermediate stage orchard, commercial stoolbed cooperator, and biotic and abiotic stress
screening trials.

STAGE 9
Final evaluations and selections, commercial ramp-up and patent applications occur in years 25-
27 (<1 rootstock genotype).Plant material for rootstock genotypes demonstrating marked
improvement over commercially available varieties is increased in commercial stoolbeds.
Intermediate stage evaluation orchards are removed after 10th leaf.Patent and UPOV protection
applications are filed on the best Geneva series rootstock genotypes.Additional on-farm trials
are planted.

We have no plans for domestic patents on CG series rootstocks in 1999.

STAGE 10
First commercial sale of Geneva rootstocks, elimination of all unreleased genotypes from trials,
years 28-30.NC-140 and on-farm trial data collection continues.Unreleased genotypes that
showed promise but were not demonstrably superior to commercially available rootstocks are
eliminated from the program.

G.16 and G.30 are available for limited commercial plantings in 1999, G.11 and G.65 may be
commercially available in 2002.

CHALLENGES
Because of the extensive and ambitious scope of the USDA-Cornell rootstock breeding program,
and because of past problems with misidentified 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.

STRENGTHS
This program is unique among apple rootstock programs around the world because of 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 cultivatedMalus 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.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-Cornell rootstock
breeding program is recognized worldwide as a promising source of new, disease-resistant and
productive rootstock genotypes for the future.

Jim Cummins’ general strategy through the mid-1970s and early 1980s was to make
hybridizations between established rootstock cultivars with desirable horticultural characteristics
(e.g., M.9, B.9, P.2) and wild relatives of cultivated apples (e.g.,Robusta 5, Malus floribunda)
that showed strong resistance to the fire blight bacteria (Erwinia amylovora).These crosses led
to the first generation of Geneva series rootstocks including G.30 (aRobusta 5crabapple by
M.9) and G.16 (Ottawa 3 byMalus floribunda).While these genotypes show great promise in
the orchard, nursery operators often dislike Geneva series rootstocks because, like G.30 and
G.65, they can be difficult to propagate.To address these problems Dr. Cummins initiated a
second series of crosses in 1992-1994 that use the first generation cultivars with improved fire
blight andPhytophthoraspp. resistance as parents crossed again to cultivars with the
horticultural characteristics appreciated by nursery operators (e.g., M.26, P.2).The cultivars
from this second series of crosses are still in a very early stage of the breeding program and have
not yet moved to the orchard evaluation stage, but should prove very interesting.These
genotypes “in the pipeline”are what will become commercially available probably in the 2020s.