NC140: Improving Economic and Environmental Sustainability in Tree-Fruit Production Through Changes in Rootstock Use
Statement of Issues and JustificationThe NC-140 Regional Research Project is designed to address a number of high-priority areas within the North Central Region and in North America. This project seeks to enhance economically and environmentally sustainable practices 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, 2010). Specifically, this project addresses high priorities defined by NCRA 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 disciplines in multiple states. 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 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.
With the highly competitive international market, the demand for high quality fruit by consumers, the strong pressure to reduce chemical use, and a need to enhance the economic efficiency of production, tree-fruit growers must look to economically and environmentally sustainable management schemes of production. Growers who want to stay profitable must establish high-density plantings with smaller trees using new cultivars. These high-density plantings cost 10 to 20 times more per land area to establish than lower-density plantings, thus greatly enhancing economic risk. Potential returns of high-density plantings, however, far exceed those of low-density plantings, particularly during the first 10 years. The central component of a high-density system is the rootstock, the part of the tree which provides control of final tree height allowing for closer tree spacing and greater number of trees per land area. As part of the tree, the rootstock influences many factors in addition to tree size, particularly productivity, fruit quality, pest resistance, stress tolerance, and ultimately profitability. However, size-controlling rootstocks are lacking for many fruit crops, and those rootstocks that are available have inherent weaknesses. Past research has successfully identified size controlling and early bearing rootstocks for apple and cherry, but inefficient rootstocks remain a problem for other tree fruits. 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 choices for growers.
Success with new orchard systems depends on reliable recommendations that are based on sustained research. New pome- and stone-fruit rootstocks cannot be recommended unless there is coordinated multi-site research investigating soil and climatic adaptability, root anchorage, size control, precocity, productivity, pest resistance, and propagation. Tree fruits are long-lived perennials, so a minimum of eight years is necessary to obtain an indication of rootstock performance and to accurately assess the potential for improved profitability, reduction of external farm inputs, and enhancement of production efficiency. With ever-increasing use of high density systems, there is a concomitant demand by growers for research that solves problems and for timely information that prevents costly mistakes.
A stable tree-fruit industry based on economically and environmentally sustainable orchard systems is one of the primary goals of NC-140 research. Knowledge of rootstock performance has led to research-based recommendations that have been adopted by the industry and have led to increasingly efficient orchard systems. Prior to organization of NC-140, knowledge of rootstock performance and adaptability was obtained from unrelated studies resulting in serious planting and management errors thus a loss in revenue. Evaluating rootstock tolerances to biological, environmental, and edaphic stresses requires uniform, cooperative testing. New rootstocks are quickly and systematically exposed to widely varying soil and climatic conditions to shorten the time necessary for thorough continental evaluation.
Any newly developed rootstock must exist as an integrated orchard-management system. Current economic trends make production efficiency of multi-genetic plant combinations in various management systems one of the most important factors that must be evaluated thoroughly before specific combinations are recommended for large-scale plantings by fruit growers. Uniform trials replicated within sites and across varying climatic and edaphic conditions have been established by the NC-140 Committee.
Orchard systems, focusing on the rootstock, must be designed to meet the specific needs of each temperate-zone tree fruit crop. One of these needs is the high cost and scarcity of labor. In response, the apple and cherry industries have developed high density orchard systems with a smaller trees and a higher number of trees per acre, with all tree maintenance occurring from the ground using size controlling rootstocks. High density systems were originally developed in Europe with rootstocks adapted to a European climate. Research done by NC140 members demonstrated growth characteristics of rootstocks under North American conditions were different than in northern Europe, with tree responses varying greatly across regions in North America. Meanwhile, rootstock breeding programs have resulted in many new elite selections that may be better adapted to the range of North American environmental conditions. These new rootstocks combined with new management systems require testing under many North American climates and modifications of training and pruning techniques must be developed to match local growing conditions.
If the temperate-zone fruit industry is going to continue to remain competitive in international markets and meet the needs of the consuming public, new genetic material will need to be incorporated to enhance performance. Through traditional plant breeding and novel genetic engineering methods, researchers can incorporate insect and disease resistance into existing rootstock material, as well as develop rootstocks with enhanced horticultural performance. Obtaining genetic material from research programs from throughout the world and testing those new rootstocks through the NC-140 cooperators has been an integral part of the project. Clonal materials of different rootstocks have been obtained from many countries since the inception of the NC-140 project and will continue. Rootstocks developed with new genetic engineering techniques can also be tested efficiently and effectively within the committee structure.
With many new rootstocks available for growers and nurseries, the need to be able to identify these plants via morphological and molecular methods is imperative. Some rootstocks stand out morphologically because of a difference in bark and leaf characteristics, but most do not. Developing methods for use in the laboratory and in the field will help all who use rootstocks to decrease the likelihood of planting mistakes.
One of the major roadblocks that limits industry access to new rootstocks is the very slow propagation time that is characteristic of clonal rootstocks. New rootstocks are available in small numbers because it takes several years to propagate a sufficient number of plants for rapid multiplication. Research on alternative ways to quickly propagate rootstocks is very much needed to shorten the time when these rootstocks will have a positive impact on the industry.
Low temperatures, soil adaptability, and susceptibility to pests limit the use of some existing rootstocks, and potentially will limit the adaptability of some new rootstocks in North America. Studies should include factors contributing to stress tolerance, controlling various stresses, or rapidly screening potential genotypes for susceptibility or tolerance. A better understanding of the physiological mechanisms behind these responses may allow for development of cultural practices, which can relieve the detrimental effects of stress and expand production into previously suboptimum soils and climates.
Outreach will continue to be integral to the project. Using eXtension, members of NC-140 will expand availability of information electronically, in addition to regional and local web sites. Additional outreach efforts will continue including written material for growers and other stakeholder groups, on-site educational programs in individual states and at national and international grower and scientific meetings
Cooperative testing of new and existing rootstocks by NC-140 researchers continues to generate interest and support from the fruit and nursery industries. This interest has resulted in industry financial support for the establishment of cooperative plantings, grants for state rootstock research, and propagation of trees for several of the NC-140 plantings. Individual researchers will 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 estimated that over the term of the current project (2012-2017), nearly $2,000,000 will be received to support NC-140 research from sources other than universities, Hatch funds, and RRF funds, and more than one half of this total will come from grower organizations.
Uniform trial plantings, supported by local industry growers, have been used in the past as research sites in which researchers collected preliminary or critical data to support objectives of competitive extramural grant projects and proposals. For example, early trial work in apples identified an apple rootstock, B.9, which demonstrated little to no Fireblight infection of the scion canopy in field plots. Researchers at Cornell University used this site and field observations to launch more in-depth research, funded by larger competitive grants demonstrating and confirming the effects of B.9 in suppressing disease pathogenesis.
The proposed research will enhance economic viability of farms through improved selection of rootstocks leading to greater production efficiency and improved fruit quality. Orchards may use labor and land more efficiently leading to a faster return on investment with fewer tree losses.
A compelling need exists for these coordinated studies and to initiate new research on a large scale for temperate-zone fruit tree rootstocks as new plant materials are made available. Continued testing will provide a thorough evaluation of promising rootstocks, multiple genetic systems, and planting and training system efficiencies. This research project has and will continue to lead to sound recommendations to growers and nurseries based on widespread knowledge of adaptability and performance of plant material.
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