NC140: Improving Economic and Environmental Sustainability in Tree-Fruit Production Through Changes in Rootstock Use
(Multistate Research Project)
NC140: Improving Economic and Environmental Sustainability in Tree-Fruit Production Through Changes in Rootstock Use
Duration: 10/01/2017 to 09/30/2022
Statement of Issues and Justification
The NC-140 Regional Research Project addresses economically and environmentally sustainable development in temperate fruit production by focusing on rootstocks and root systems. The NC-140 project meets the guidelines presented by the North Central Regional Association (NCRA) in Guidelines for Multistate Research Activities (July, 2014) by addressing high priorities within the crosscutting research areas of agricultural production, processing, distribution, genetic resource development and manipulation, integrated pest management, and economic development and policy. The project involves researchers and extension specialists from multiple disciplines in multiple states as well as international collaborators. Researchers involved in this project have leveraged federal and state dollars to add significant financial and in-kind resources to address this important research area. Lastly, outreach is integrated within the project and includes electronic information transfer through web sites, written material for growers and other stakeholder groups, on-farm demonstrations, and numerous educational programs conducted at a local, national and international level.
Needs Identified by Stakeholders
The needs of the stakeholders addressed in this project have been identified through various sources and surveys. Many of the members of this project have Cooperative Extension appointments and serve as educational liaisons with the tree fruit industries in their respective states working directly with their stakeholders in identifying and addressing needs. Additionally, a national needs assessment was initiated in 2009 to identify research needs of tree fruit growers. Between 2009 and 2012, multiple meetings of tree fruit representatives, including growers, allied industries, researchers, and extension specialists were held. Through this process a list of stakeholder research and extension priorities was compiled. Among the greatest needs identified were integration of rootstocks into management systems, and root and soil interactions (replant/soil-borne problems); these are encompassed in the updated NC-140 objectives.
Importance of the Work and Consequences if it is Not Done.
Tree-fruit growers must adopt economically and environmentally sustainable orchard management strategies to remain competitive in both national and international markets, to meet consumer demand for high quality fruit, to address the pressure to reduce chemical use, and to enhance production efficiency. The root system, or rootstock, is a key orchard component to address these issues. The rootstock provides control of tree vigor and final tree size, allowing for closer tree spacing and more trees per land area resulting in high density plantings. Higher density plantings lead to earlier production and greater yield potentials. To stay profitable, growers must establish higher-density orchards of cultivars in demand by consumers and having higher market values. However, establishment costs for high-density orchards are 10 to 20 times more per land area than lower-density plantings, thus greatly increasing economic risk. Potential economic returns of high-density orchards, however, can far exceed orchards at a lower-density, particularly during the first 10 years. Past NC-140 research has successfully identified reliable size-controlling, early-bearing rootstocks for apple and cherry, and led to the integration of their use in high-density production systems to reduce tree size, labor costs and significant tree and/or production losses from disease and environmental stresses. Although size-controlling rootstocks are currently in the relatively early stages of development for peaches, pears, apricots, and plums, this project seeks to identify and evaluate potential size-controlling rootstocks and associated orchard strategies to increase production and sustainability in these tree fruits as well.
In addition to tree size, the rootstock profoundly affects sustainable productivity, fruit quality, pest resistance, amenability to mechanization technologies, adaptability to different soil types, stress tolerance, and ultimately profitability. Many commercially available rootstocks have inherent weaknesses and have not been evaluated thoroughly for potential problems in different production environments. Continued tree losses due to cold temperature injury, disease, scion incompatibility, and poor soil conditions are an economic cost for the industry that can be ameliorated by improving rootstock genotype options. There is a concomitant demand by growers for timely research that solves production problems and provides information for the prevention of costly mistakes.
Success with new orchard systems depends on reliable recommendations for a wide range of conditions which can be best accomplished with coordinated multistate research. Since the inception of the NC-140 project, U.S. tree fruit growers have received reliable rootstock recommendations that have transformed their industry into one of the most productive in the world. New pome- and stone-fruit rootstock recommendations are based on multi-site research investigating soil and climatic adaptability, root anchorage, size-control, precocity, productivity, and pest resistance. Tree fruit are long-lived perennial plants, so a minimum of eight years is necessary to develop a thorough understanding of rootstock performance and to accurately assess the potential for improved profitability, reduction of grower inputs, and enhancement of production efficiency. With multi-state research, new rootstocks are quickly and systematically exposed to widely varying soil and climatic conditions to shorten the time necessary for a thorough evaluation as well as to help develop site specific recommendations across this range of growing environments. Consequently, the vast majority of growers rely on research-based NC-140 recommendations as their primary resource for rootstock selection.
Changes in orchard systems have occurred over the past ten years to address profitability and the increasingly high cost and shortage of labor. Using size-controlling rootstocks, the apple and cherry industries have adopted high-density orchard systems that facilitate tree maintenance operations from the ground or mobile platforms, eliminating dangerous ladder use. Increased adoption of mechanization, and even the exploration of robotics, for pruning and harvesting is also underway, which is influenced by the orchard system implemented. Consumer interest in new varieties of apple, pear, peach, plum, apricot, and cherry creates a demand for highly productive and precocious rootstocks and an opportunity for growers to select rootstocks that are better adapted to these industry changes and to regional climate and soil considerations.
If the U.S. temperate-zone tree fruit industry is going to remain competitive in international markets and meet increasing consumer demands, new genetic materials will need to be identified, evaluated, and adopted to address emerging problems. Through traditional plant breeding methods and novel genomic tools, researchers have incrementally incorporated insect and disease resistance into existing rootstock germplasm, as well as developed rootstocks with enhanced horticultural performance and stress tolerance. Obtaining potentially improved rootstock genotypes from research programs throughout the world for testing by NC-140 cooperators has been an integral part of the project. Promising clonal materials for new rootstocks for pear, peach, apricot, plum, and cherry have been obtained both domestically and internationally. Development and use of genetic markers can speed up the selection process, but are dependent on coordinated evaluation of economically important traits in multiple environments. Meanwhile, rootstock breeding programs have generated many new elite selections that may be preferentially adapted to specific regions of North America. These new rootstocks require coordinated testing under diverse North American climates and soil types, and training and pruning techniques must be modified to match rootstock traits with local growing conditions.
Advantages of a Multistate Effort
Collaborative research by the NC-140 project team has demonstrated that tree fruit rootstock growth characteristics can differ widely across North American production regions. Low or high temperatures, soil conditions, and susceptibility to endemic pests can limit the adaptability of some rootstocks in certain regions. A greater understanding of stress factors and physiological mechanisms behind these responses, as well as rapid screening of genotypes for susceptibility or tolerance, will improve tree survival and productivity in diverse soils and climates.
Outreach is integral to the NC-140 project (http://www.nc140.org/). Using eXtension, in addition to regionally and state-focused web sites, NC-140 members will expand the digital availability of rootstock information. Other outreach efforts will include written materials for growers and other stakeholder groups, as well as video and on-site educational programs in individual states and at national and international grower and scientific meetings. On-farm research and demonstration trials, including farm tours and field days, are very effective for disseminating NC-140 research results directly to growers.
Collaborative evaluation of new and existing rootstocks by NC-140 researchers continues to generate financial support from fruit and nursery industries for the propagation and establishment of cooperative plantings, as well as grants for specific rootstock research. Individual researchers use support from industry as seed money to leverage and seek state, federal and private foundation grants (competitive and non-competitive) for associated studies. It is anticipated that over the term of the current project (2012-2017), approximately $2,000,000 will have been generated to support NC-140 research as seed funding/matching and/or direct support from sources other than universities, Hatch funds, and RRF funds, and more than half of this total will come from grower organizations. Additionally, more than $4 million in USDA-SCRI funding has recently been procured (by a team that includes NC-140 members) for intensive apple rootstock-related studies that are dependent upon the existing NC-140 trials as a unique research resource.
As evidenced in the previous work and performance of this project, the proposed and on-going research will enhance the economic viability of growers through improved selection of rootstocks that lead to greater production efficiency and improved fruit quality. Orchard labor and land will be utilized more efficiently, with fewer tree losses to pests and environmental stresses, leading to a faster and greater return on investment.
A compelling need exists to initiate new coordinated research on a large scale for temperate-zone fruit tree rootstocks as new genetic materials are developed or made available. Many new rootstocks will require a change in orchard cultural practices. Continued testing will provide a thorough evaluation of promising rootstocks, multiple genetic systems, and planting and training system efficiencies. This research project will continue to develop sound research-based recommendations for growers and nurseries that are based on extensive and collaborative multi-state work, providing an increased understanding of rootstock adaptability and performance.
Related, Current and Previous Work
Rootstocks have been used to facilitate or improve the performance of desirable fruiting cultivars for thousands of years with the earliest documentation in 412 B.C. (Mudge et al., 2009). Despite considerable advances in technology and markedly different driving factors, the development of improved rootstocks will be critical to the future economic sustainability of North America’s tree fruit industry (Elkins et al., 2012; Reighard, 2013). Stakeholder profitability will depend on orchards that are uniform, yield efficient, stress tolerant and markedly less reliant on labor; subsequently, new orchards must be compatible with automation and mechanization technologies (Robinson, 2008). Indeed, orchard systems have become highly-structured and increasingly intensive over a relatively short time span for apple (Dorigoni et al., 2011; Robinson et al., 2011), pear (Robinson and Dominguez, 2015), and sweet cherry (Du et al., 2012; Lang et al., 2014; Law and Lang, 2016; Long et al., 2015; Musacchi et al., 2015). These innovative and highly-profitable systems both capitalize and depend on the rootstocks’ ability to confer precocity, improve flowering habits (Maguylo et al., 2004), alter ripening and fruit quality (Marini et al., 2008) and impart dwarfing (Vercammen, 2004) to the scion. No single rootstock is widely adapted to the diverse soil and climatic conditions of North America; therefore, a suite of new rootstocks is required to provide alternatives for new cultivars and emerging production challenges (e.g., labor, environmental sustainability [replant chemicals], pest threats, climate change, etc.). The role of the NC-140 project is to develop and/or acquire and test the performance of novel rootstocks via coordinated, long-term field trials comprising diverse sites, modern training systems and relevant cultivars with emphases on production efficiency, disease resistance and stress tolerance/avoidance.
Elucidation of the mechanisms regulating fundamental traits and physiological behaviour of rootstock and rootstock/scion interactions is central to advancing rootstock science. The study of these systems is complex, given that fruit trees are compound genetic plants (Koepke and Dhingra, 2013) and interactions often exist between rootstocks and scions (Tworkoski and Miller, 2007) that accumulate over time (DeJong et al., 2011). Scion vigor, for example, was affected by the xylem structure and anatomy of the rootstock (DeJong et al., 2013; Solari and DeJong, 2006; Tworkoski and Fazio, 2011). Graft transmissible agents regulated scion physiology of apple (Kanehira et al., 2010; Xu et al., 2010) and peach (Reighard et al., 2001). Rootstock-modulated changes in gene expression of scions were correlated with dwarfing and hormone relations of sweet cherry (Prassinos et al., 2009) and apple (Li et al., 2012; Jensen et al., 2010, 2011). Novel technology like gene transfer to impart pathogen resistance (Aldwinckle et al., 2009; Malnoy et al., 2010; Song et al., 2013) may indeed play an important role in the development of the next generation of rootstocks and underscores the value of identifying molecular mechanisms and markers (Fazio et al., 2011; Rusholme et al., 2004, 2008) to allow for improved genetic material and earlier selection. For example, identification of genomic loci associated with dwarfing in pear (Wang et al., 2011) and apple (Celton et al., 2009; Fazio et al., 2014) has the potential to markedly decrease the time to discovery. Whether rootstock improvements are realized via traditional breeding or transgenic approaches, field performance trials will be a prerequisite to industry adoption and acceptance by consumers.
Concomitant with breeding efforts, the acquisition of novel germplasm from international sources has led to improved tree fruit performance. Promising new tree-fruit rootstocks possessing superior attributes to standard genotypes are continually being introduced from worldwide sources (DeJong et al., 2011; Elkins et al., 2012; Hrotkó, 2016; Khanizadeh et al., 2011; Univer et al., 2011; Zhang et al., 2011; Zurawicz et al., 2011, Reighard et al., 2013). Evaluation of the diverse germplasm housed at the USDA-National Clonal Germplasm Repositories, for example, has markedly decreased the time required to advance new materials such as cold-hardy quince rootstocks for pear production (Einhorn et al., 2011) and apple germplasm with resistance to fungal components of replant disease (Fazio et al., 2009). For the latter, selection of progeny from Malus sieversii crosses represent the future of apple rootstocks. Replant disease has been characterized as a high priority by many fruit growers as regulations on chemical fumigants become increasingly stricter (Mazzola et al., 2009). New apple rootstocks adaptable to replant disease facilitate sustainable production practices and improve the efficiency and profitability of new plantings (Robinson et al., 2003). Subsequently, field evaluation of apple rootstocks with purported tolerance to replant disease is ongoing throughout various regions of the US (Auvil et al., 2011; Parker et al., 2011; St. Laurent et al., 2010). In addition, major advances in apple rootstock resistance to fire blight (LoGiudice et al., 2006; Norelli et al., 2003), woolly apple aphid and powdery mildew (Fazio et al., 2006; Russo et al., 2007) have all been documented. Virus tolerance of sweet cherry dwarfing rootstocks (Lankes, 2011) and peach rootstock resistance to Armillaria and peach tree short life (Beckman, 2011) are all burgeoning areas of research. Development of genotypes resistant or tolerant to biotic stresses is fundamental to the sustainable management of tree fruit.
Research efforts have also focused on improved resistance to abiotic stresses. Anticipated changes in climate (Cai et al., 2014) underscore the need for increased efficiency in resource acquisition (e.g., nutrient and water; Fazio et al., 2013; Jimenez et al., 2013; Neilsen et al., 2015; Tworkowski et al., 2016). Rootstocks directly affect the mineral nutrition of scion fruits and leaves (Fallahi et al., 2013a, 2013b; Neilsen and Hampson, 2014; Reighard et al., 2013). Rootstock imparted tolerance or sensitivity to cold stress has been evaluated under episodic events (Warmund et al., 2002) and in controlled-environments to simulate sub-freezing conditions for pear (Einhorn et al., 2011) and apple (Privé et al., 2001, Moran et al., 2011). For pear, over 20 genotypes of quince have been observed to possess sufficient hardiness for northern regions. Pear production in North America cannot adopt the precocious, dwarfing quince rootstocks commonly used in Europe due to freeze sensitivity. Consequently, little progress has been made with Pyrus rootstock germplasm over the past few decades (Azarenko, et al., 2000; Einhorn et al., 2013; Elkins et al., 2012). The ability for rootstocks to tolerate abiotic stresses not only results in greater profitability but potentially facilitates the expansion of production into marginal climates or sites.
The NC-140 project has inarguably benefited growers and nurseries by critically evaluating new rootstocks that have transformed the industry principally through dissemination of information via eXension, multiple state web sites of cooperators, and regional, national and international grower educational meetings and publications. The proposed objectives will sustain efforts to improve the competitive stance of the North American tree fruit industry.
CRIS and NIMSS searches were conducted and this work will enhance the prior body of work and will not duplicate any research. Please see attachment for detailed information on the CRIS and NIMSS searches.
To evaluate the influence of rootstocks on temperate-zone fruit tree characteristics grown under varying environments and training systems using sustainable management practices.
To develop improved rootstocks for temperate-zone fruit trees, including breeding, using phenomic and genomic tools and acquisition of new rootstocks from global sources.
To investigate physiological processes, biotic and abiotic stresses and scion/rootstock interactions on tree growth and productivity.
To integrate and disseminate research-based information that facilitates successful stakeholder adoption of rootstock technologies.
To evaluate the influence of rootstocks on temperate-zone fruit tree characteristics grown under varying environments and training systems using sustainable management practices, established replicated uniform trials will be maintained, and new trials will be established across North America. Promising new and existing rootstocks as a compound genetic system will be selected and evaluated for survival, precocity, productivity, size control, anchorage, suckering, pest resistance, adaptability, and production efficiency.
Data will be collected according to protocols established by the technical committee. For each trial, data collected will include root suckering, tree growth as measured by changes in trunk cross-sectional area, tree height, canopy spread, precocity, yield, yield efficiency, and fruit size. Trials will be formally concluded after 8-10 growing seasons. Designated coordinators will collect and archive data for the life of each trial for all sites. Data will be processed and annual progress reports shared with trial cooperators and the full membership at annual meetings. Trials are established by cooperators and coordinated by representatives from MA (2010 Honeycrisp apple, 2010 Fuji apple and 2015 Organic Modi Apple), MI (2010 sweet cherry systems, 2012 pear, 2013 pear, 2017 Benton sweet cherry, 2017 Montmorency tart cherry, 2018 apple, and 2018 pear), ONT (2014 apple), and SC (2009 Redhaven peach and 2017 Cresthaven peach). Standard statistical analyses will be performed on all data, and trials will be summarized for publications after five and 8-10 years of testing.
Plantings under active evaluation or proposed for future establishment are as follows:
(a) 2009 Peach. In 2009, a peach rootstock trial was established with Redhaven as a scion cultivar at 16 locations (AL, CA, CH, CO, GA, IL, KY, MA, MO, NC, NYx2, PA, SC, and UTx2). Rootstocks included were Viking, Atlas, BH-5, Empyrean 1, Guardian, Lovell, KV010123, KV010127, Krymsk 86, Fortuna, Empyrean 3, Empyrean 2, HBOK 10, HBOK 32, Prunus americana, Krymsk 1, and Controller 5.
(b) 2009 Peach Physiology. Ion 2009, a trial was established with three cultivars (Crimson Lady, Redhaven and Cresthaven) at 14 locations (AL, AR, CA, GA, ID, KY, MD, NJ, NY, NC, SC, and UT) to evaluate peach fruit size potential and fruit quality under varying environmental conditions.
(c) 2010 Sweet Cherry Systems. In 2010, a sweet cherry rootstock and training systems trial was established with Benton (CA, IN, MI, and OH), Skeena (BC, CH, and NS), Regina (NYx2), and Bing (OR) as scion cultivars. Rootstocks (Gi3, Gi5, and Gi6) were included in all combinations with training system (tall spindle, UFO, and KGB at all sites, plus super slender axe at MI and NY).
(d) 2010 Honeycrisp Apple. In 2010, an apple rootstock trial was established with Honeycrisp as a scion cultivar at 13 locations (BC, CH, CO, IL, IA, MA, MN, MI, NJ, NS, NY, OH, and WI). Rootstocks included B.9, B.10, B.7-3-150, B.7-20-21, B.67-5-32, B.64-194, B.70-6-8, B.71-7-22, G.11, G.41N, G.41TC, G.202N, G.202TC, G.935N, G.935TC, CG.2034, CG.3001, CG.4003, CG.4004, CG.4013, CG.4214, CG.4814, CG.5087, CG.5222, PiAu 51-11, PiAu 9-90, Supp.3, M.26 EMLA, M.9 Pajam 2, and M.9 NAKBT337.
(e) 2010 Fuji Apple. In 2010, an apple rootstock trial was established with Aztec Fuji as a scion cultivar at six locations (CH, ID, KY, NC, NY, PA, and UT). Rootstocks included B.9, B.10, B.7-3-150, B.7-20-21, B.67-5-32, B.64-194, B.70-6-8, B.71-7-22, G.11, G.41N, G.41TC, G.202N, G.202TC, G.935N, G.935TC, CG.2034, CG.3001, CG.4003, CG.4004, CG.4013, CG.4214, CG.4814, CG.5087, CG.5222, PiAu 51-11, PiAu 9-90, Supp.3, M.26 EMLA, M.9 Pajam 2, and M.9 NAKBT337.
(f) 2012 Pear. In 2012, a pear rootstock trial was established in OR d’Anjou as the scion cultivar. Rootstocks included the Amelanchier clones A1, A4, and A7 compared to OH×F 87.
(g) 2013 Pear. In 2013, a pear rootstock and training system trial was established with Bosc (NY), Bartlett (CA), and d’Anjou (OR) as scion cultivars. Rootstocks at each site included Pyro 2-33, OH×F 87 and OH×F 69. Rootstocks were combined with three training systems (Bi-axis, tall spindle, and perpendicular V) and each system and rootstock combination were planted at 1, 1.5 or 2 m in-row spacing at all locations.
(h) 2014 Apple. In 2014, an apple rootstock trial was established at multiple locations in the U.S. (AL, GA, ID, MA, ME, MI, MN, NJ, NY, PA, SC, UT, VA, WA, WI), Mexico and Canada (Ontario: Ridgetown and Simcoe) including trees on M.9, M.26, V.1, V.5, V.6, V.7, G.41, G.935, G.30, G.11, G.202, G.9809, and B.10 grafted to Honeycrisp and Fuji.
(i) 2015 Organic Modi Apple. In 2015, an apple rootstock trial was established with Modi as the scion in certified organic blocks at 15 North American locations (CA, CO, ID, IA, MA, MI, NJ, NM, NS, NYx 2, VT and WI). Rootstocks included were G.11, G.16, G.30, G.41, G.202, G.214, G.222, G.890, G.935, G.969, and M.9 NAKBT337.
(j) 2017 Peach. In 2017 a peach rootstocks trial will be established in AL, CO, GA, MI, NC, NY, ONT, PA, SC, and UT. Rootstocks include Controller 6, 7 and 8 (UC Davis); Rootpac 20 (Densipac) and Rootpac 40 (Nanopac) from Agromillora Iberica; MP-29 (USDA-Georgia); Control(s) Lovell and/or Guardian® (Clemson/USDA). The scion cultivar is Cresthaven.
(k) 2017 Sweet Cherry. In 2017, a sweet cherry rootstock trial will be established with Benton as the scion cultivar at 6 locations across the U.S. Rootstocks will include Gi5 and new or previously untested introductions such as Gi3, Gi12, MSU Cass, MSU Clare, MSU Clinton, MSU Crawford, and MSU Lake and MXM 14.
(l) 2017 Tart Cherry. In 2017, a tart cherry rootstock trial will be established with Montmorency as the scion cultivar at 4 locations across the U.S. Rootstocks will include mahaleb, Gi5, and new or previously untested introductions such as Gi12, MSU Cass, MSU Clare, MSU Clinton, MSU Crawford, and MSU Lake.
(m) 2018 Pear. In 2018, a pear rootstock trial will be established at 5 locations across the U.S. and Canada. Rootstocks included new cold-hardy quince rootstocks, among others.
(n) 2018 Apple. In 2018, an apple rootstock trial will established with CrimsonCrisp and/or Buckeye Gala as the scion(s) in approximately 12 locations across the U.S. and Canada. Rootstocks to be included are 2 Malling rootstocks, 3 new New Zealand selections and 7 Geneva rootstocks.
(o) 2019 Plum and Apricot. In 2019, a plum and apricot rootstock trial will be established at approximately 6 locations across the U.S. and Mexico. Rootstocks will include new U.S. and European introductions.
(p) 2020 Sweet Cherry. In 2020, a sweet cherry rootstock trial will be established with Lapins at 8 locations across North America. Rootstocks will include Gi5 and new or previously untested introductions such as Gi13, Gi17, WeiGi1, WeiGi2, WeiGi 3, PiKu 1, PiKu 3, MSU Crawford, Krymsk 5, and Krymsk 6.
(q) 2020 Tart Cherry. In 2020, a tart cherry rootstock trial will be established with Montmorency at 5 locations across North America. Rootstocks will include mahaleb, Gi5, and new or previously untested introductions such as Gi13, Gi17, WeiGi1, WeiGi2, WeiGi 3, PiKu 1, PiKu 3, Krymsk 5, and Krymsk 6
Other multi-state/province rootstock trials will be conducted on a regional basis, but will not involve the entire committee in the coordination. However, these will be reported as being under the work of NC-140. Tree performance in the projects will be evaluated as in previously mentioned rootstock trials. These projects include the following.
(a) 2010 Tart Cherry Systems. In 2010, two separate tart cherry rootstock x training systems trials were established with Montmorency at MI (Gi3, Gi5, Gi6, Mahaleb, and Montmorency on its own roots) and UT (Gi3, Gi5, Gi6, and Mahaleb), with 3 high density training systems studied at each site.
(b) 2013 Vineland Apple. In 2013, an apple rootstock trial was established in ON, NS, and BC comparing Honeycrisp trees on V.5, V6, V.7, M.9 and M.26.
NC-140 participants will continue individual research studies to evaluate important aspects of performance and physiology as they relate to apple rootstocks and training systems: (1) evaluation of G.11, G.16, CG.2034, G.41, CG.4213, CG.4214, CG.5012, CG.5087, CG.5463, CG.5890, G.935, and M.9 NAKBT337 (PA); (2) evaluation of G.30, CG.7037, CG.7480, CG.8534, and M.7 EMLA (PA); (3) evaluation of G.41, G.935, and M.9-Nic 29 with Honeycrisp and Scifresh (PA); (4) evaluation of B.9 and Fuji on M.9 NAKBT337 trained to tall spindle, vertical axis, tall trellis or minimally pruned (PA); (5) evaluation of PFR1, PFR2, and PFR5 and two Geneva control rootstocks with Honeycrisp (PA); (6) evaluation of Geneva rootstocks under high pH conditions (CO); (7) determination of sustainability, efficiency, productivity, and winter hardiness of SnowSweet and Minneiska apples on B.9, G.16, G.30, M.26 EMLA, M.7 EMLA, M.9 NAKBT337, V.1 and V.3 (MN); (8) evaluation of 31 rootstocks (IN); (9) evaluation of 47 Geneva rootstocks, with B.9 and 3 Malling stocks as controls (NY); (10) evaluation of 39 CG rootstocks, 4 Japan Morioka stocks, 4 PiAu stocks, 2 JTE stocks B.118, O.3 and 5 Malling stocks (NY); (11) evaluation of the performance of 11 apple rootstocks (G.16, G.11, G.41, G.4210, G.30, G.935 G.6210, M.9, B.9, M.26 and M.7) in 4 different orchard training systems (tall spindle, slender axis, vertical axis and slender pyramid) planted in a range of tree densities using 3 apple cultivars (NY); (12) evaluation of the performance 6 Geneva rootstocks (G.16, G.41, G.11, G.935, G.6210 and G.30) along with M.9, M.26, M.7 and B.118 as controls in 4 high density orchard systems (vertical axis, triple axis, tall spindle and super spindle) (NY); (13) evaluation of 34 Geneva rootstocks, 3 Malling controls, B.9, Vineland 1, Ottawa 3 and P.22 (NY); (14) evaluation of 42 Geneva rootstocks, 4 Malling controls, B.9, B.118 and Mark (NY); (15) evaluation of 4 Geneva rootstocks and 3 Malling controls (NY); (16) evaluation of 32 Geneva rootstocks, 6 Malling controls, 5 Budagovsky (B), 1 PiAu and 1 Vineland (V) (NY); (17) evaluation of M9.T337and B.9 on four training systems (PA); (18) evaluation of four training systems, bi-axis at two densities, tall spindle and upright fruiting shoots with M.9T337 (PA).
NC-140 participants will continue individual research studies to evaluate various aspects of performance and physiology as they relate to peach rootstocks and training systems: (1) evaluation of Controller 5, Controller 9, Krymsk 1, Krymsk 2, MRS 2/5, Penta, and Tennessee Natural (PA); (2) evaluation of the HBOK/Controller series (CA).
NC-140 participants will continue individual research studies to evaluate various aspects of performance and physiology as they relate to cherry rootstocks and training systems: (1) high density orchard evaluation of tart cherry on Gi3, Gi5 and Gi6 rootstocks (UT); (2) evaluation of the performance of 4 cherry rootstocks (Gi5, Gi6, Gi12 and Mazzard) in 4 different orchard training systems (vertical axis, Spanish bush, quad axis and central leader) with 3 sweet cherry cultivars (NY); evaluation of tart cherry on various dwarfing rootstocks in high density orchards for over-the-row mechanical harvest in grower orchards (MI, UT); evaluation of sweet cherry canopy orientation, densities, and productivity relative to variations in rootstock vigor (MI).
NC-140 participants will continue individual research studies to evaluate various aspects of performance and physiology as they relate to pear rootstocks and training systems: (1) evaluation of selections of Amelanchier as a potential pear rootstock (MI, OR); (2) establishment of a pear systems trial of 3 rootstocks, 3 training systems, and 3 spacings (CA, NY, OR); (3) evaluation of the performance of 6 pear rootstocks (seedling, OHxF97, OHxF87, Pyrodwarf, Pyro2-33 and Quince) in 4 training systems (central leader, vertical axis, tall spindle and super spindle) planted in range of tree densities using 4 pear cultivars (NY).
To develop improved rootstocks for temperate-zone fruit trees, including breeding, using phenomic and genomic tools and acquisition of new rootstocks from global sources. Traditional and marker-assisted breeding programs will develop improved rootstocks for apples (NY), cherry (MI), peaches (GA, SC), and pears (WA). Each of these breeding program directors will provide progress reports regarding the results of their work to be shared at annual meetings with committee members. Where possible and needed, cooperators and members of the committee may serve as second- or third- phase testing sites for confirmation of biotic stress resistance. Eventually, progeny identified as having promise from these programs will enter the uniform trial testing process as described in Objective 1. Additionally, manuscripts or their published citations will be shared with the members at-large, regarding results from these studies.
Specific objectives of the breeding programs include: (1) peach rootstock tolerance or resistance to root-knot nematodes (GA), peach tree short life complex (GA, NC), and Armillaria root rot (GA, SC); (2) cherry rootstock tolerance or resistance to Armillaria (MI); (3) mapping the Prunus genome (MI, SC) and isolate markers for nematode and Armillaria resistance to use in breeding programs (SC); (4) development of new rootstocks for cherry trees, based on genotypes generated and selected from the sour cherry variety breeding program (MI); (5) development of an understanding of the genetic mechanisms underlying important rootstock traits (dwarfing, precocity and disease resistance) using a segregating/mapping population from an interspecific apple rootstock cross (O.3 x Robusta 5 - designated O3R5), both on their own roots and with Gala as a scion (data from trees on their own roots and those with Gala will be combined with a genetic molecular marker map with the potential of using markers for screening for specific traits) (NY/USDA-ARS Geneva Breeding Program); (6) pear parental germplasm has been established and will be used to start Pyrus rootstock breeding focusing on vigor control and resistance to various biotic and abiotic stresses (WA).
To investigate physiological processes, biotic and abiotic stresses and scion/rootstock interactions on tree growth and productivity, studies will be conducted by individual members and cooperators at various institutions to elucidate stress tolerance of fruit trees as influenced by rootstocks. Basic rootstock performance data will be collected as part of the evaluation of rootstocks in the trials listed under objective 1; however, additional, more-detailed studies will be led and conducted by individual cooperators using these rootstock plantings as uniform multiple test sites. Trial coordinators or cooperators will canvas cooperators to determine interest in conducting separate, more detailed studies on each specific parameter. Those leading the effort will supply progress reports and updates regarding the results of their work to be shared with colleagues collecting the data and it will be shared with the full membership at annual meetings. Additionally, manuscripts or their published citations will be shared with the members at-large, regarding results from these studies. Stress-related studies will include the following.
Low-temperature stress: (1) assessment of the effects of various rootstocks on low-temperature susceptibility of peach flower buds (GA, MO); (2) evaluation of the influence of apple rootstocks (B.9, M.9 and M.27) and scions (SunCrisp and Fuji) on blackheart injury and determine the relationship between blackheart and fruit yield (MO); (3) determine the cold hardiness of rootstocks and the influence of rootstock on scion cold hardiness for apple (IA, ME, MI, MN, ONT, UT); (4) evaluation of peach rootstocks on scion cold hardiness (CO, GA, UT); and (5) evaluation of cold resistance of quince rootstock for pear (OR,MI).
General climate, water, nutritional, and physiological stress: (1) study the relationship between rootstocks, soil, climate, moisture and nutrient uptake for apple and cherry (BC); (2) evaluation of the relationship of apple rootstock, nutrient uptake and fruit quality and disorders such as bitter pit (ID, MI, NY, WA); (3) evaluation of peach, apple, and cherry rootstocks on alkaline soil (NM, UT); (4) evaluation of tart cherry rootstocks with and without irrigation (WI); (5) evaluation of cherry rootstock effects on water and nutrient relationships (MI); (6) development of climate-modifying systems, such as high tunnels in cherry and other stone fruits and the relationship to rootstock performance (MI); (7) evaluate the impact of apple rootstock/scion combinations on fruit sunburn and crop load management (WA).
Biotic stress: (1) evaluation of several inoculation techniques to accelerate field evaluations of Armillaria resistance of peach rootstocks (GA); (2) evaluation of peach tree short life (GA, NC, SC), Armillaria (GA, SC), and root-knot nematode resistance (GA, SC); (3) evaluate Armillaria resistance of cherry rootstocks (MI); (4) study the effects of rootstocks on apple replant disease (CO, NC, NJ, NY); (5) evaluation of rootstocks for organic cultivation (CO); (6) evaluation of the effects of rootstock on fire blight in apple (MD, MI, NY, PA); (7) evaluation of tomato ringspot virus (TRSV) tolerance and resistance of rootstocks ( 32 Geneva rootstocks, 6 Malling controls, 5 Budagovsky, 1 PiAu and 1 Vineland) with Ace Spur Delicious as the scion cultivar (NY); (8) evaluation of the tolerance and resistance to TRSV of 34 Geneva rootstocks, 4 Malling controls, and 1 Budagovsky rootstock with Super Chief Delicious as the scion cultivar (VA), and (9) evaluation of the relationships among rootstock, scion and fire blight susceptibility in Asian pears (AL).
To integrate and disseminate research-based information that facilitates successful stakeholder adoption of rootstock technologies. In 2010, an eXtension Community of Practice (CoP) was funded through USDA-SCRI, and initiated to assemble the vast quantity of apple-related information developed by NC-140 and other apple-related research. The Apple eXtension website was launched in September 2011. This novel vehicle for information collection, organization and delivery will be developed further during the period of this project.
Participants will assist in developing articles to increase access to information generated from this research project and serve as experts answering questions when they arise (AL, CO, IA, ID, IL, MA, MI, MN, MO, NC, NJ, NS, NY, OH, PA, UT, WA).
Measurement of Progress and Results
- At least 15 refereed articles will be published, including eight interim and seven final trial reports, all based on the NC-140 coordinated regional research trials.
- Approximately 150 additional articles will be published by NC-140 members, based on NC-140-related research. These will include refereed and non-refereed articles targeted for scientific and fruit grower audiences.
- New tree fruit rootstocks will be introduced from North American breeding programs under the guidance of NC-140 (Anticipate 10 rootstocks).
- New tree fruit rootstocks will be introduced from international breeding programs to North American fruit growers with detailed recommendations regarding their suitability for various production areas, anticipate approximately 25 rootstocks.
- NC-140 research results will be communicated in 50 papers at scientific conferences and in 300 presentations to grower audiences.
- The NC-140 (www.nc140.org) and the eXtension Apple (articles.extension.org/apples) websites will continue to be developed and updated to provide NC-140 results to all stakeholders, as will individual NC140 member websites, blogs, and other social media outlets.
Outcomes or Projected Impacts
- NC-140 recommendations and educational programs will guide the planting of 200,000+ acres of fruit trees in the next 5 years in North America, resulting in a more economically and environmentally sustainable fruit industry, and a broad range of affordable, nutritious fruit selections for consumers.
- By utilizing NC-140 recommended rootstocks and orchard production systems, growers will receive significantly earlier returns on investments related to tree establishment, achieving an average break-even point on investment at 5 years after planting.
- By utilizing NC-140 recommended rootstocks and orchard production systems, mature yields will increase by 20% per acre, fruit size by 10%, and the percent meeting the highest grade category by 20%, compared to 10 years ago.
- By utilizing NC-140 recommended rootstocks and orchard production systems, orchard labor efficiency will increase by 20% per acre, compared to 10 years ago.
- The annual financial benefit to U.S. fruit growers from earlier returns, greater yield, higher fruit quality, and more efficient use of labor will be $250,000,000 as a direct result of the implementation of NC-140 recommendations.
- The use of NC-140 recommended dwarfing rootstocks will result in a 50% reduction in canopy volume and a concomitant 50% reduction in pesticide usage on 200,000 acres. The reduction in pesticide use will yield environmental benefits and save $150,000,000 in pesticide cost and application.
- The use of NC-140 recommended dwarfing rootstocks will result in a 50% reduction in canopy volume, thereby facilitating increased use of orchard covering systems to protect tree fruit crops from damaging climatic events such as hail, rain, wind-bruising, and/or frost damage. Adoption of such systems will increase by 5,000 acres from 2017-2022.
- The use of NC-140 recommended disease-resistant and stress tolerant rootstocks will lead to a decline in annual tree losses by 10%.
- By utilizing NC-140 coordinated genomic and phenomic tools for rootstock breeding, the efficiency of development and selection of next generation tree fruit rootstocks will be enhanced, leading to the testing and release of more new apple, peach, cherry, and pear rootstocks with significantly improved traits.
- Cumulative state and federal investment in NC-140 will be about $15,000,000. Cumulative, measurable benefits to the U.S. temperate tree-fruit industries will be more than $400,000,000. Less easily measured benefits, such as averted losses and enhanced environmental quality, will increase the financial value of NC-140 to well beyond $500,000,000 in the next 5 years.
Milestones(2017):Objective 1 timeline: • 2017-22: All on-going coordinated trials will be maintained with data collected annually until trial completion (see Methods), and interim and final reports generated accordingly; new coordinated trials will be established as materials are acquired and propagated (Attachment). 2017: 2010 Sweet Cherry Systems Interim report; 2009 Peach Physiology final report; 2017 Sweet Cherry, 2017 Tart Cherry and 2017 Peach trials established. 2018: 2013 Pear Systems interim report; 2009 Peach trial final report; 2018 Apple rootstock and 2018 Pear rootstock trials established. 2019: 2014 Honeycrisp Apple and 2014 Fuji Apple interim reports; 2009 Pear final report; 2019 Apricot/Plum trial established. 2020: 2015 Organic Modi Apple interim report; 2010 Sweet Cherry Systems, 2010 Honeycrisp Apple and 2010 Fuji Apple trials final reports; 2020 Sweet Cherry and 2020 Tart Cherry trials established. 2021: 2021 Apple trial established. 2022: 2017 Sweet Cherry, 2017 Tart Cherry and 2017 Peach interim reports; 2013 Pear Systems trial final report.
(2022):Objective 2 timeline: • 2017-22: New rootstock genotypes will be released throughout the project duration and incorporated into the coordinated trials detailed in Attachment • 2017-22: New rootstocks from international breeding programs will be acquired throughout the project duration and incorporated into the coordinated trials detailed in Attachment.
(2022):Objective 3 timeline: • 2017-22: All coordinated trials detailed in Objective 1 and Attachment include the evaluation of site-specific biotic and abiotic stresses. As appropriate, this information will be interpreted for dissemination along with other rootstock evaluation traits. • 2017-22: Supplemental studies of tree developmental, reproductive, or environmental stress physiology will be conducted by individual NC-140 cooperators based on national need and research expertise. Results from these analyses will be reported to NC-140 annually and will be published or presented to scientific and/or grower audiences as appropriate.
Projected ParticipationView Appendix E: Participation
The NC-140 project is committed to rapidly disseminating research-based results and information to the stakeholder groups it serves, commercial orchardists, small-scale orchardists, fruit-tree nursery operators, industry representatives, professional colleagues, county extension educators, and home gardeners, master gardeners, and consumers.
Results from each state and province will be communicated at the annual technical committee meeting and posted online at the project web site, www.nc140.org. The site contains cooperator contact information, annual reports/minutes, rootstock research planting descriptions, report summaries, and research results. Results include refereed publication abstracts, links to journals for the full article, links to trade magazines, extension newsletter articles, and PowerPoint or pdf files of poster and professional talks. Outreach efforts have been enhanced with formal participation in eXtension for Apples, www.extension.org/apples. This website broadens the access to results and information generated from this project.
Results are made available in refereed journals, grower publications, major national trade publications (print and electronic format), and extension publications (print and electronic) prepared by each state participant; oral presentations at professional meetings (i.e. American Society for Horticulture Science and the International Society for Horticulture Science) as well as national and international fruit grower meetings. Numerous presentations will be made annually at regional, state and local fruit-grower meetings (clientele and stakeholders) and producer field days sponsored by state extension programs, often in conjunction with state horticulture associations. In addition, cooperators will publish articles including results and recommendations in appropriate extension newsletters, fact sheets, and experiment station production manuals and bulletins.
This regional Technical Committee will be organized for the North Central Region as outlined in the Guidelines for Multistate Research Activities. The executive committee shall consist of the chairperson, vice chairperson, secretary, immediate past chairperson, the coordinator of each NC-140 trial, and the crop committee chairs. Each year, a secretary will be elected to serve for one year, and the past vice-chairperson and the secretary will advance to the next higher office commencing in January. Members of the executive committee will set the annual meeting agenda, write and distribute the minutes and annual report, and act on the Technical Committee’s behalf as necessary. An Administrative Advisor will act as an advisor to the Technical Committee on procedures and policies related to regional research and provide coordination and communication with other regional projects and the North Central Directors. Annual meetings will be held for the purpose of evaluating current work, planning future work, and coordinating publications which may result from the work undertaken in the regional project. Each year, the chairperson will be responsible for organizing and the leading the annual meeting, the vice chairperson will submit the annual report, and the secretary will submit the meeting minutes.
For uniform coordinated projects established under Objectives 1-4, coordinators will be appointed on a continuing basis to coordinate the trials: Reighard (SC)-2009 Peach, 2017 Peach; Marini (PA)-2009 Peach Physiology; Autio (MA)-2010 Apple, 2015 Organic Modi Apple; Einhorn (MI)-2012 Pear, 2013 Pear, 2018 Pear, 2018 Apple; Cline (ONT)-2014 Apple; Lang (MI)- 2010 Sweet Cherry, 2017 Sweet Cherry, 2017 Tart Cherry. These coordinators will provide technical oversight concerning those plantings, maintain contact with the participants through correspondence, transmit pertinent information to participants and the Committee to insure uniformity of the studies, prepare data collection forms and details of coordinated procedures which will permit a consolidation of the research findings, assemble and analyze combined data or summarize data previously analyzed, initiate all publications regarding the planting, and report annually to the Committee on progress of the planting.
Standing committees for each major crop will be appointed to plan, acquire plant genotypes, and organize propagation of trees for future multi-location uniform trials: Musacchi (WA)-apple; Reighard (SC)-peach; Einhorn (MI)-pear; and Lang (MI)-cherry.
The Hatch Multi-State Research Funds expended on NC-140 (among all the cooperating states) will leverage approximately $2,000,000 of additional funds from various granting organizations, including Federal and state agencies, local grower organizations, and the International Fruit Tree Association. The Executive Committee will oversee funding requests in support of NC-140.
Aldwinckle, H., E. Borejsza-Wysocka, P. Abbott, and S. Kuehne. 2009. Transformation of apple for disease resistance: Evolving strategies. Phytopathology. 99: S191-S191.
Auvil, T.D., T.R. Schmidt, I. Hanrahan, F. Castillo, J.R. McFerson, and G. Fazio. 2011. Evaluation of dwarfing rootstocks in Washington apple replant sites. Acta Horticulturae. 903: 265-271.
Azarenko, A., Anderson, R., Brown, G., Embree, C., Ferree, D., Gaus, A., Hunter, D., Kappel, F., Ketchie, D., Meilke, E., Renquist, R., and Sugar, D. 2000. Final evaluation of the NC-140 national rootstock trial. ISHS 8th International Pear Symposium: 90 (abstract).
Beckman, T.G. 2011. Progress in developing Armillaria resistant rootstocks for use with peach. Acta Horticulturae. 903: 215-220.
Cai, S., Zidek, J.V., Newlands, N.K., and Neilsen, D. 2014. Statistical modeling and forecasting of fruit crop phenology under climate change. EnvironMetrics 25: 621-629.
Celton, J.M., D.S. Tustin, D. Chagne, and S.E. Gardiner. 2009. Construction of a dense genetic linkage map for apple rootstocks using SSRs developed from Malus ESTs and Pyrus genomic sequences. Tree Genetics & Genomes. 5: 93-107.
DeJong, T.M., R.S. Johnson, and K.R. Day. 2011. Controller 5, Controller 9 and Hiawatha peach rootstocks: their performance and physiology. Acta Horticulturae. 903: 221-228.
DeJong, T. M., S. Tombesi, B. Basile and D. Da Silva. 2013. Beakbane and Thompson (1939, East Malling) had it right: scion vigour is physiologically linked to the xylem anatomy of the rootstock. Aspects of Applied Biology 119: 51-58.
Dorigoni, A., P. Lezzer, N. Dallabetta, S. Serra, and S. Musacchi. 2011. Bi-axis: an alternative to slender spindle for apple orchards. Acta Horticulturae. 903: 581-588.
Du, X., Chen, D., Zhang, Q., Scharf, P.A., Whiting, M.D. 2012. Dynamic responses of sweet cherry trees under vibratory excitations. Biosystems Engineering. 111: 305-314.
Einhorn, T., Postman, J., and Turner, J. 2011. Characterization of cold hardiness in quince: Potential pear rootstock candidates for Northern pear production regions. Acta Horticulturae 909: 137-144.
Einhorn, T., Castagnoli, S., Smith, T., Turner, J., and Mielke, E. 2013. Summary of the 2002 Pacific Northwest Pear Rootstock Trials: Performance of ‘d’Anjou’ and ‘Golden Russet Bosc’ pear on eight Pyrus rootstocks. J. Amer. Pom. Soc. 67: 80-88.
Elkins, R.B.and T.M. DeJong. 2011. Performance of 'Golden Russet Bosc' pear on five training systems and nine rootstocks. Acta Horticulturae. 903: 689-694.
Elkins, R., R. Bell, and T. Einhorn. 2012. Needs assessment for future US pear rootstock research directives based on the current state of pear production and rootstock research. J. Amer. Pom. Soc. 66:153-163.
Elkins, R.B., S. Castagnoli, C. Embree, R. Parra-Quezada, T.L. Robinson, T.J. Smith and C.A. Ingels. 2011. Evaluation of potential rootstocks to improve pear tree precocity and productivity. Acta Horticulturae. 909: 183-194.
Fallahi, E., B. Fallahi, and B. Shafii. 2013a. Irrigation and rootstock influence on water use, tree growth, yield, and fruit quality at harvest at different ages of trees in ‘Pacific Gala’ apple. HortScience. 48:588-593.
Fallahi, E., K. Arzani, and B. Fallahi. 2013b. Long-term leaf mineral nutrition in ‘Pacific Gala’ apple (Malus domestica Borkh.) as affected by rootstock type and irrigation system during six stages of tree development. Journal of Horticultural Science & Biotechnology 88 (6) 685–692.
Fazio, G., H.S. Aldwinckle, R.P. McQuinn, and T.L. Robinson. 2006. Differential susceptibility to fire blight in commercial and experimental apple rootstock cultivars. Acta Horticulturae. 704: 527-530.
Fazio, G., H.S. Aldwinckle, T.L. Robinson, and Y. Wan. 2011. Implementation of molecular marker technologies in the Apple Rootstock Breeding program in Geneva - challenges and successes. Acta Horticulturae. 903: 61-68.
Fazio, G., H.S. Aldwinckle, G.M. Volk, C.M. Richards, W.J. Janisiewicz, and P.L. Forsline. 2009. Progress in evaluating Malus sieversii for disease resistance and horticultural traits. Acta Horticulturae. 814: 59-66.
Fazio, G., D. Kviklys, M. Grusak, and T. Robinson. 2013. Phenotypic diversity and QTL mapping of absorption and translocation of nutrients by apple rootstocks. Aspects of Applied Biology 119:37-45.
Fazio, G., Y. Wan, D. Kviklys, L. Romero, R. Adams, D. Strickland and T. Robinson. 2014. Dw2 a new dwarfing locus in apple rootstocks and its relationship to induction of early bearing in apple scions. J. Amer. Soc. for Hort. Sci. 139:87-98.
Hrotkó, K., 2016. Potentials in Prunus mahaleb L. for cherry rootstock breeding. Scientia Horticulturae, 20:70-78.
Jensen, P.J., I. Makalowska, N. Altman, G. Fazio, C. Praul, S.N. Maximova, R.M. Crassweller, J.W. Travis, and T.W. McNellis. 2010. Rootstock-regulated gene expression patterns in apple tree scions. Tree Genetics & Genomes. 6: 57-72.
Jensen, P.J., T.W. McNellis, N. Halbrendt, J.W. Travis, N. Altman, C.A. Praul, S.N. Maximova, R.M. Crassweller, and I. Makalowska. 2011. Rootstock-regulated gene expression profiling in apple trees reveals genes whose expression levels are associated with fire blight resistance. Acta Horticulturae. 903: 87-93.
Jimenez, S., J. Dridi, D. Gutierrez, D. Moret, J.J. Irigoyen, M. Moreno, and Y. Gogorcena. 2013. Physiological biochemical and molecular responses in four Prunus rootstocks submitted to drought stress. Tree Physiology 33:1061-1087.
Kanehira, A., K. Yamada, T. Iwaya, R. Tsuwamoto, A. Kasai, M. Nakazono, and T. Harada. 2010. Apple phloem cells contain some mRNAs transported over long distances. Tree Genetics & Genomes. 6: 635-642.
Khanizadeh, S., Y. Groleau, R. Granger, G.L. Rousselle, J.P. Prive, and C.G. Embree. 2011. St Jean Morden (SJM) dwarf winter hardy rootstock series. Acta Horticulturae. 903: 191-192.
Koepke, T. and A. Dhingra. 2013. Rootstock scion somatogenetic interactions in perennial composite plants. Plant Cell Reports. 32: 1321-1337.
Lang, G.A., S. Blatt, C. Embree, J. Grant, S. Hoying, C. Ingels, D. Neilsen, G. Neilsen and T. Robinson. 2014. Developing and evaluating intensive sweet cherry orchard systems: The NC140 regional research trial. Acta Horticulturae. 1058:113-120.
Lankes, C. 2011. GiSelA cherry rootstocks compared for virus tolerance and field performance. Acta Horticulturae. 903: 521-527.
Lankes, C.and G. Baab. 2011. Screening of apple rootstocks for response to apple proliferation disease. Acta Horticulturae. 903: 379-383.
Law, T.L. and G.A. Lang. 2016. Planting angle and meristem management influence sweet cherry canopy development in the upright fruiting offshoots training system. HortScience. 51: 1010-1015.
Li, H.L., H. Zhang, C. Yu, L. Ma, Y. Wang, X.Z. Zhang, and Z.H. Han. 2012. Possible roles of auxin and zeatin for initiating the dwarfing effect of M9 used as apple rootstock or interstock. Acta Physiologiae Plantarum. 34: 235-244.
LoGiudice, N., Fazio, G., Robinson, T.L., Aldwinckle, H.S. 2006. The nature of resistance of the 'B.9' apple rootstock to fire blight. Acta Horticulturae. 704:515-519.
Long, L., G. Lang, S. Musacchi, and M. Whiting. 2015. PNW 667 cherry training systems. Pacific Northwest Extension Publication. 667.
Maguylo, K., Lang, G.A., and Perry, R.L. 2004. Rootstock genotype affects flower distribution and density of `Hedelfinger sweet cherry and `Montmorency sour cherry. Acta Horticulturae. 636:259-266.
Malnoy, M., E.E. Boresjza-Wysocka, J.L. Norelli, M.A. Flaishman, D. Gidoni, and H.S. Aldwinckle. 2010. Genetic transformation of apple (Malus x domestica) without use of a selectable marker gene. Tree Genetics & Genomes. 6: 423-433.
Marini, R.P., R. Moran, C. Hampson, M. Kushad, R.L. Perry, and T.L. Robinson. 2008. Effect of dwarf apple rootstocks on average 'Gala' fruit weight at six locations over three seasons. J. Amer. Pom. Soc. 62: 129-136.
Mazzola, M., J. Brown, X. Zhao, A. Izzo, and G. Fazio. 2009. Interaction of Brassicaceous seed meal and apple rootstock on recovery of Pythium spp. and Pratylenchus penetrans from roots grown in replant soils. Plant Disease. 93: 51-57.
Moran, R.E., Y. Sun, F. Geng, and D. Zhang. 2011. Cold temperature tolerance of one- and two-year old apple rootstocks. HortScience 46: 1460-1464.
Mudge K., J. Janick, S. Scofield, and EE Goldschmidt. 2009. A history of grafting. In: Janick, J (ed) Horticultural Reviews. John Wiley & Sons Inc., NJ, pp 437-439.
Musacchi, S., F. Gagliardi, and S. Serra. 2015. New training systems for high-density planting of sweet cherry. HortScience. 50: 59-67.
Neilsen, G. and Hampson, C. 2014. ‘Honeycrisp’ apple leaf and fruit nutrient concentration is affected by rootstock during establishment. J. Amer. Pom. Soc. 68: 178-189.
Neilsen, G.H., Neilsen, D., Guak, S., and Forge, T.A. (2015). The effect of deficit irrigation and crop load on leaf and fruit nutrition of fertigated Ambrosia/M.9 apple. HortScience. 50: 1387-1393.
Norelli, J.L., Holleran, H.T., Johnson, W.C., Robinson, T.L., and Aldwinckle, H.S. 2003. Resistance of Geneva and other apple rootstocks to Erwinia amylovora. Plant Disease. 8:26-32.
Parker, M.L., D. Ritchie, and G.L. Reighard. 2011. Guardian peach rootstock performance and preplant soil fumigation effects in a fallow site. Acta Horticulturae. 903: 469-473.
Prassinos, C., J.H., Ko, G. Lang, A.F., Iezzoni, and K.H., Han. 2009. Rootstock-induced dwarfing in cherries is caused by differential cessation of terminal meristem growth and is triggered by rootstock-specific gene regulation. Tree Physiology. 29: 927-936.
Privé, J.P., Zhang, M.I.N., Embree, C., and Hebb, D. 2001. The influence of freeze-thaw cycling in cold hardiness studies on apple rootstocks. Acta Horticulturae. 557:123-130.
Reighard, G.L. 2013. Peach, plum and apricot rootstocks for the 21st century. Aspects of Applied Biology 119:59-66.
Reighard, G.L., W. Bridges, B. Rauh and N.A. Mayer. 2013. Prunus rootstocks influence peach leaf and fruit nutrient content. Acta Horticulturae 984:117-124.
Reighard, G.L., Ouellette, D.R., and Brock, K.H. 2001. Modifying phenotypic characters of peach with graft transmissible agents. Acta Horticulturae. 557:163-167.
Robinson, T.L. and L. Dominguez. 2015. Yield and profitability of high-density pear production with Pyrus rootstocks. Acta Horticulturae. 1094: 247-256.
Robinson, T., Aldwinckle, H., Holleran, T., and Fazio, G. 2003. The Geneva series of apple rootstocks from Cornell: performance, disease resistance, and commercialization. Acta Horticulturae. 622:513-522.
Robinson, T.L. 2008. The evolution towards more competitive apple orchard systems in the USA. Acta Horticulturae. 772: 491-500.
Robinson, T.L., S.A. Hoying, and G.H. Reginato. 2011. The tall spindle planting system: principles and performance. Acta Horticulturae. 903: 571-579.
Rusholme, R.L., S.E. Gardiner, H.C.M. Bassett, D.S. Tustin, S.M. Ward, and A. Didier. 2004. Identifying genetic markers for an apple rootstock dwarfing gene. Acta Horticulturae: 405-409.
Rusholme-Pilcher L, Celton JM, Gardiner SE. 2008. Genetic markers linked to the dwarfing trait of apple rootstock ‘Malling 9’. J. Amer. Soc. Hort. Sci. 133, 100–106.
Russo, N.L., T.L. Robinson, G. Fazio, and H.S. Aldwinckle. 2007. Field evaluation of 64 apple rootstocks for orchard performance and fire blight resistance. Hortscience. 42: 1517-1525.
Solari, L.I., and T.M., DeJong. 2006. The effect of root pressurization on water relations, shoot growth, and leaf gas exchange of peach (Prunus persica) trees on rootstocks with differing growth potential and hydraulic conductance. Journal of Experimental Botany. 57: 1981-1989.
Song, G.-Q., K.C. Sink, A.E. Walworth, M.A. Cook, R.F. Allison, and G.A. Lang. 2013. Engineering cherry rootstocks with resistance to Prunus necrotic ring spot virus through RNAi-mediated silencing. Plant Biotechnology Journal doi: 10.1111 / pbi.12060.
St. Laurent, A., I.A. Merwin, G. Fazio, J.E. Thies, and M.G. Brown. 2010. Rootstock genotype succession influences apple replant disease and root-zone microbial community composition in an orchard soil. Plant and Soil. 337: 259-272.
Tworkoski, T. and G. Fazio. 2011. Physiological and morphological effects of size-controlling rootstocks on 'Fuji' apple scions. Acta Horticulturae. 903: 865-872.
Tworkoski, T. and S. Miller. 2007. Rootstock effect on growth of apple scions with different growth habits. Scientia Horticulturae. 111: 335-343.
Tworkoski, T., G. Fazio, and D.M. Glenn, 2016. Apple rootstock resistance to drought. Scientia Horticulturae 204:70-78
Univer, T., N. Univer, and K. Tiirmaa. 2011. The results of the Estonian apple rootstock breeding program. Acta Horticulturae. 903: 151-157.
Vercammen, J. 2004. Dwarfing rootstocks for sweet cherries. Acta Horticulturae. 658:307-311.
Wang, C., Y., Tian, E.J., Buck, S.E., Gardiner, H. Dai, and Y. Jia. 2011. Genetic mapping of PcDw determining pear dwarf trait. J. Amer. Soc. Hort. Sci. 136: 48-53.