STATEMENT OF ISSUES AND JUSTIFICATION:  

The NC-140 Regional Research Project addresses economically and environmentally sustainable improvement in temperate fruit production by focusing on rootstocks and root systems. The project meets the guidelines presented by the North Central Regional Association (NCRA) in Guidelines for Multistate Research Activities (August 2017) 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. 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 diverse educational programs conducted at local, national, and international levels for stakeholders and peer scientists.

 Needs Identified by Stakeholders

The needs of the stakeholders addressed in this project have been identified through periodic regional and national 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 to identify and address needs. Additionally, through the NIFA-USDA-SCRI and USDA-SCBG programs, multiple meetings have been held with tree fruit representatives, including growers, allied industries such as packing houses and nurseries, researchers, and extension specialists. Through this process, a list of stakeholder research and extension priorities has been compiled and updated periodically. Among the critical needs identified were the identification of rootstocks with specific traits that: optimize production of consumer-preferred varieties like 'Honeycrisp' apple; facilitate labor- and input-efficient orchard systems; and can alleviate problematic root and soil interactions (e.g., replant disease, high pH, etc.). As residential developmental pressure on desirable orchard land (and its associated upward pressure on land prices) continues to increase, sustaining fruit production in some regions often requires establishing new orchards in sites with less-than-ideal soil conditions. All these needs 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 regional, 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 is a key orchard component that can impact these issues, and tree fruit growers address these issues by utilizing the genetic traits of rootstocks, onto which the fruiting varieties are grafted. Rootstocks can provide a range of tree vigor control and final tree size when matched to optimize local soil and climatic conditions, allowing for higher density plantings with smaller trees that are more efficient per unit of land area. Higher density plantings facilitate earlier production and greater cumulative yield potentials, but also must provide appropriate vigor for the site so that canopy shade and pruning do not become excessive. To be profitable, growers must establish high-density orchards with appropriate rootstocks grafted to cultivars that are in demand by consumers and have high market value. 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. Grafting to a rootstock inappropriate for the regional climate or orchard soil type can be economically disastrous. Potential economic returns from high-density orchards can far exceed that of low-density orchards, particularly during the first 10 years. Past NC-140 research successfully identified reliable size-controlling, early-bearing rootstocks for apple and cherry, and has 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. Size-controlling rootstocks for peaches, pears, apricots, and plums are now in their relatively early stages of development, concomitant with potentially major changes in tree training as they are integrated into more efficient and productive orchard systems.

 In addition to tree size, the rootstock profoundly affects canopy training strategies that impact fruit quality, pest and disease resistance, labor efficiency, and amenability to mechanization technologies, as well as adaptability to different soil types, stress tolerance, and ultimately sustainable productivity and profitability. Among these, potential advances in orchard mechanization technologies have changed dramatically in the past 5 years, with the introduction of imaging technologies for orchard mapping, crop load quantification, plant stress detection, selective "smart" spray applications, and even robotic harvesters. The precision of such technologies is tied closely to smaller, simpler tree canopies facilitated by vigor-controlling rootstocks. Yet, many commercially available rootstocks also have inherent weaknesses and have not been evaluated thoroughly for potential problems in different production environments. Tree losses due to low temperature injury, disease, scion incompatibility, and adverse soil conditions are an economic cost for the industry that can be ameliorated by improving rootstock genotype knowledge and options.

Furthermore, rootstock resiliency to changing climate and more frequent extreme climatic events is an increasing concern. Over the past 5 years, many production regions have experienced both periodic drought conditions as well as excessive rainfall events that cause temporary flooding. Where drought conditions have persisted even across years, irrigation water availability increasingly may be curtailed. Tree fruit growers and nurseries demand timely research that anticipates and solves production problems and provides information that can prevent costly mistakes, given the long-term (25+ year) investment for establishing orchards and new orchard technologies. A warming climate has been manifested in later leaf senescence in the fall and earlier budbreak in the spring, subjecting temperate zone tree fruits to increased risk of tissue damage from fall and spring freeze events. Similarly, the more variable climate can negatively affect cold acclimation and de-acclimation as well as the winter chilling hour accumulation required for the transition of endormancy to ecodormancy, subsequently affecting healthy bud break and flowering in spring. Rootstock genotype can significantly influence these canopy responses to the environment, and evaluation of rootstocks must place a greater emphasis on characterizing these responses across North America's diverse tree fruit production regions.

 This next phase of the NC-140 project will continue to identify and evaluate rootstocks for critical genetic traits that include size-control and adaptation to different soils and climates. Project research will lead the evolution of orchard systems as new rootstocks are integrated into orchard strategies and technologies to increase production, reduce labor, improve fruit quality and yields, and facilitate environmental sustainability across the range of temperate zone tree fruit production.

 Technical Feasibility

Success with new orchard systems depends upon reliable research-based recommendations for a wide range of production conditions that can only be accomplished with coordinated multistate research. Since the inception of the NC-140 project, North American tree fruit growers have received critical 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 upon multi-site research investigations of soil and climatic adaptability, root anchorage, size-control, precocity, productivity, and pest resistance. Tree fruit are long-lived perennials, 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 which shortens the time necessary for a thorough evaluation and the development of site-specific recommendations across growing environments. Consequently, the vast majority of growers rely on research-based NC-140 recommendations as their primary resource for rootstock selection. 

 Major innovations in orchard systems have occurred over the past fifteen years to address the increasingly high cost and shortage of labor, and to improve orchard yields and returns-on-investment. Using size-controlling rootstocks, apple and cherry growers have adopted high-density orchard systems that are evolving to facilitate efficiencies in orchard management, including tree maintenance operations from the ground or mobile platforms, eliminating dangerous and expensive use of ladders. Expanded mechanization is being coupled experimentally with new imaging, sensing, data acquisition, and artificial intelligence (machine learning) technologies, for greater precision in orchard management decision-making as well as potential autonomous task implementation, including robotics for selective spraying, pruning and harvesting. The successful implementation of such technologies is strongly influenced by the simplification of high density orchard systems on appropriate rootstocks. NC-140 researchers are critical partners with faculty and industry colleagues in agricultural biosystems and computer engineering for these on-going technological developments.

 If the U.S. temperate zone tree fruit industry is going to remain competitive in international markets as well as meet increasing domestic and local consumer demands, new improved genetic materials will need to be identified, tested, and adopted to address emerging problems. Through traditional plant breeding methods and novel genomic tools, NC-140 (and other) researchers have incrementally incorporated insect and disease resistance into existing rootstock germplasm, as well as developed rootstocks with enhanced horticultural performance and tolerance to environmental stresses. Obtaining putatively improved rootstock genotypes from research programs throughout the world for testing by NC-140 cooperators has been an integral part of the project. Promising new clonal rootstocks for apple, pear, peach, apricot, plum, and cherry have been obtained from domestic and international breeding programs. Development and use of genetic markers can speed up selection, but depend on coordinated evaluation of economically important traits in multiple environments. Meanwhile, rootstock breeding programs have generated many new elite selections that may show differential adaptation to specific regions of North America. These new rootstocks require coordinated testing under diverse North American climates and soil types, with training and pruning techniques modified to optimize 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 the physiological mechanisms behind these responses, as well as rapid screening of genotypes for susceptibility or tolerance to biotic and abiotic stress factors, will improve tree survival and sustain productivity in diverse soils and climates.

 Outreach is integral to the NC-140 project. Using regionally-focused extension web sites, NC-140 members continually expand the digital availability of rootstock information. Associated outreach efforts 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 extremely effective for disseminating NC-140 research results and recommended new techniques and technologies directly to growers.

 Collaborative, coordinated evaluation of new and existing rootstocks by NC-140 researchers continues to generate financial support from fruit and nursery industry partnerships for propagation and establishment of test plantings. Individual researchers use industry support as seed money to seek and leverage state, federal and private foundation grants (competitive and non-competitive) for associated rootstock studies. It is estimated that during the current project period (2017-2022), approximately $2,000,000 has 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 comes from grower organizations. Additionally, more than $7 million in USDA-SCRI funding has been procured during this period by teams that include NC-140 members for intensive apple and cherry studies that are essentially outgrowths of existing NC-140 trials that have served as unique research resources.

 Likely Impacts

As evidenced in the previous work and performance of this project, the proposed and on-going research will enhance the economic viability of tree fruit growers through improved selection of rootstocks, input-efficient rootstock management practices, and development of rootstock-facilitated orchard technologies that result in greater production efficiencies and improved fruit quality. Orchard labor and land will be utilized more efficiently, with higher sustainable yields and fewer tree losses to pests and environmental stresses, leading to a faster and greater return on investment.

The need to initiate new coordinated research studies across diverse growing environments for temperate-zone tree fruit rootstocks is compelling, as new genetic materials are developed or made available, and societal (labor availability) and climatic (changing) pressures increase for producers. Successful utilization of new rootstocks can require, or facilitate, significant changes in orchard cultural practices. Continued thorough evaluation of promising rootstocks, multiple genetic systems, and associated new mechanical and computer-aided technologies is critical for successful implementation of planting and training system efficiencies. The NC-140 research project will continue to develop 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 for economically and environmentally sustainable production.