By Robert Crassweller and James Schupp et.al.
The project seeks to enhance economically and environmentally sustainable practices in temperate tree fruit production by focusing on rootstocks.
Specifically, this project addresses high priorities within the crosscutting research areas of agricultural production, processing, and distribution, genetic resource development and manipulation, integrated pest management and economic development and policy. The project involves researchers from multiple locations and is multidisciplinary. Researchers involved in this project have leveraged federal and state dollars to add significant resources to address this research area. Lastly, outreach is integral to the project and includes electronic information transfer through web sites, written material for growers and other stakeholder groups, and numerous educational programs in individual states and at national and international grower and scientific meetings.
Over the years we have evaluated rootstocks from around the world in trial plantings across the U.S., Canada, and Mexico. Planting designs are set to be similar in all the different locations. Therefore, we can see how rootstocks perform under different geographical, climatic and regional conditions. Recently we have emphasized the evaluation of the Cornell-Geneva rootstocks due to their fire blight, Phytophthora sp. and wooly apple aphid resistance, cold hardiness, induced growth alterations to the scions, precocity, and propagation traits. The released rootstocks designated simply as Geneva or “G” have a wide range of characteristics and may or may not be suitable for the Mid-Atlantic region. The initial breeding program was started by Drs. Herb Aldwinkle and Jim Cummins of Cornell University.
Evaluation of the Geneva series in the NC-140 project began back in 1990 with a planting containing G.30 and has continued through 2019 with twelve different plantings in most of the tree fruit growing regions of North America. Each planting was evaluated and maintained for 8-10 years. Data collected included tree size, annual tree size increase, yield (number of fruit/tree as well as weight/tree), average fruit size, annual cropping efficiency, and tree survivability. Here in Pennsylvania, the establishment, maintenance and data collection of these plantings have been supported by the
State Horticultural Association of Pennsylvania Research Committee funding; without which would not have been possible for these plantings. Additional support is from
USDA NIFA and Regional research appropriations under Project 4625.
Cornell has a chart of the various Geneva rootstocks that have been released and are in commercial production. The current chart is version 4. I have modified the chart (Figure 1) to allow readers to compare the different rootstocks down the side of the table with the characteristics at the top.
In the figure, you can see that all the rootstocks are resistant to fire blight, with the majority being very resistant. Wooly apple aphid (WAA) resistance is primarily a concern in the southern hemisphere and you can see that some are not resistant. Currently, the only rootstock that may not be tolerant or replant problems is G.222. All the rootstocks are tolerant to Phytophthora sp. Some of the rootstocks have a few questions about cold hardiness. Cold hardiness of G.213 has yet to be determined. Under the rootstock suckering column G.210 and G.890 in the Cornell chart are indicated they did not sucker. However, in trials in Pennsylvania, both G.210 and G.890 have developed rootstock suckers.
The last column refers to whether the rootstock is susceptible to latent viruses in the scion cultivar. Some older cultivars have inherent viruses that can be transmitted to the rootstocks and cause poor performance of the tree. In particular, you will note that G.16, G.814, and G.935 are susceptible to scion latent viruses. This means that you should only propagate budwood or purchase trees of these rootstocks that you know are virus-free.
Figure 1. Characteristics of Geneva apple rootstocks listed alphabetically
| Rootstock | FB resist. | WAA resist. | Replant resist. | Phyto. Root Rot | Cold Hard. | Low Suckering | Virus Susc. |
|---|
| G11 | Y | N | Partial | Tolerant | Y | Y | N |
| G16 | Y | N | Partial | Tolerant | Y midwinter Early bad | Y | Y |
| G202 | VR | HIGH | Tolerant | Tolerant | Y in mid-winter | Y | N |
| G210 | VR | HIGH | Tolerant | Tolerant | Y | N/Y | N |
| G213 | VR | HIGH | Tolerant | Tolerant | TBD | Y | N |
| G214 | VR | HIGH | Tolerant | Tolerant | Y | M | N |
| G222 | VR | HIGH | N | Tolerant | Y | M | N |
| G30 | VR | N | Tolerant | Tolerant | Y | Y | N |
| G41 | VR | HIGH | Tolerant | Tolerant | Y | Y | N |
| G814 | VR | N | Tolerant | Tolerant | Y | Y | Y |
| G890 | VR | HIGH | Tolerant | Tolerant | Y | N/Y | N |
| G935 | VR | N | Tolerant | Tolerant | Y | Y | Y |
| G969 | VR | HIGH | Tolerant | Tolerant | Y | Y | N |
We have also noticed that tree performance is influenced by tree quality and size at planting. Larger trees at planting tend to remain larger and produce earlier in the years after planting. When comparing your plantings be sure that scion vigor is similar; Fuji will always produce larger trees than Honeycrisp. Soil vigor and care during site preparation will also impact tree performance.
The following are some comments and observations that we have noted from the NC-140 trials with the Geneva rootstocks:
- G.11 has performed consistently well at Rock Spring trials and appears to be on the larger size of M.9T337
- G.16 is a little smaller than M.9T337; but seems to have fewer problems with fruit developing bitter pit. Should note that it is sensitive to cultivars with latent viruses. There is some variability in tree size for G.16 depending upon planting location. G.16’s growth habit is narrow and may lend itself well to tall spindle training.
- Trees on G.41 seem to have a brittle graft union that can easily break when planting and should, therefore, be staked/supported immediately. G.41 was not impressive in the 2010 Fuji planting at Rock Springs but is doing well in a 2016 planting of Honeycrisp
- G.890 while having deep growing roots, may be too vigorous for high-density tall spindle systems.
- For weaker growing cultivars like Honeycrisp, G.969 looks to be a better choice because of fewer root suckers than G.890.
- G.202, despite some unfavorable reviews, seems to be a very grower friendly tree growth, but may have smaller fruit.
- G.935 produces uniform size trees across many sites; however, it is imperative that virus-free scions must be utilized.
- G.210 was slightly smaller than M.26 but did produce many root suckers with Golden Delicious. However, this rootstock had the highest yields and very good production efficiency.
- The big question is if any of the G.200’s or G.935 could serve as potentially semi-free-standing trees if the central leader is headed each year. (However, heading each year will delay fruit production.)
- G.214 shows good promise as does G.814, albeit we suggest that you only plant them in small quantities until more is known.
Currently, we are involved in a study to look if any of these rootstocks may influence the uptake or distribution of mineral nutrients like Ca or K relating to the development of bitter pit.
We are continuing the evaluation of new rootstocks with plantings established in 2017-18 with two strains of Honeycrisp and 2019 with Buckeye Gala. These two have new rootstock introductions developed in New Zealand. Early results of these plantings are reported in the February 2020 issue of the PA Fruit News.
If you are interested in learning more about the history and development of the Geneva rootstocks go to:
Table 1. Selected nurseries and Geneva rootstocks they propagate trees on, as of December 2019. Rootstocks are listed numerically and not by tree size.
Adams County Nursery
Boyer's
Brandt's
C&O
Cameron
Cummins
- G11
- G16
- G202
- G210
- G222
- G30
- G41
- G890
- G935
- G969
ProTree
Sierra Gold
- G11
- G202
- G210
- G214
- G222
- G30
- G41
- G814
- G890
- G935
- G969
Stark Bros.
TRECO
- G11
- G41
- G202
- G210
- G214
- G890
- G935
- G969
Van Well
Waffler
Willow Drive
- G11
- G202
- G210
- G214
- G41
- G890
- G935
- G969
(This is a brief synopsis of the presentation made at the 2020 Mid Atlantic Fruit and Vegetable Conference)
Source : psu.edu