The need as indicated by stakeholders

The scale of horticultural fruit production across North America is highly variable, ranging from large-scale farms and fruit storages in states such as Michigan, New York and Washington, to smaller sized operations in states such as Maine, Maryland, and Pennsylvania. While large scale farms and storage operations are the backbone of the USA food supply, an exciting trend towards increased diversification has been occurring nationwide, independent of production size; the expanded cultivation of many small fruits and fruit-type vegetables yields fruits for local markets is coupled with the development of new techniques for growing season extension and organic production and handling practices. The 'locavore' trend is gradually reshaping the economics of the agriculture industry and is spurring a revival of small farms; the last available report (2015) from the USDA Economic Research Service estimates that locally grown foods generated nearly $7 billion in sales in 2012. Also, the organic food industry in the U.S. has been growing at a rate of 20-30% per year for the past 10 years, with a commensurate increase in land farmed under certified organic management.

Fruits, along with vegetables, are essential components of a healthy diet, and their consumption is associated with decreased risk of chronic diseases and in maintaining a healthy weight.  Despite the widespread availability of fresh fruit, many Americans fall short of the recommended five servings per day.  The foremost complaint of consumers is lack of variety and quality in fruit – if it doesn’t taste good, no one will eat horticultural products, no matter how ‘good’ it is for their health.  Therefore, deterioration of quality attributes such as texture and flavor, as well as development of storage disorders and rots, continues to cause losses for producers and marketers, especially with increased environmental variability during growing seasons.  Environmental stressors such as high solar irradiance leading to postharvest disorders can reduce product quality in certain high production regions of the US more than others.  As a result, the fresh fruit industries rely on prophylactic postharvest chemical applications to ensure minimization of losses due to ripening, softening, senescence, decay, and development of storage disorders. While advances have been made in nontoxic control alternatives, changes in the types and amounts of available chemicals and increased emphasis on improved targets for sustainability have created a need to modify storage technologies.  New approaches are required to meet needs of organic markets, minimize losses of fruit during storage and transport, and thereby maintain regional and global market shares for domestic producers as well as allow small-scale producers to maintain local market share. A better understanding of relationships between postharvest physiology of fruits and their susceptibility to physiological disorders and decay pathogens is essential for developing improved control measures and reducing chemical use.  It also leads to improved phenotyping for new cultivar development and means for assessing disorder risk to better inform cold chain decisions and reduce disorders on the retail shelf.

This project involves research on a wide variety of fruits that are important in different growing regions.  These fruits include avocados, blueberries, cherries, papaya, peaches, pears, pineapples and plums, with the most collaborative focus on apple fruit, the most valuable fruit crop in most of the participating states.  Research with all of these specialty crops is critical to the project’s success, and sharing of technical knowledge, especially about application of new technologies, increases the probability of successful outcomes from research on all fruits. Also, while this project primarily addresses the needs of large-scale fruit storage operations, the knowledge obtained is adaptable to meet the needs of smaller-scale operations. The project involves most postharvest scientists in the USA and Canada, nearly all with extension/outreach responsibilities, thereby providing a powerful platform for development and extension of this knowledge.

Several developments in fruit production and storage technologies make this project highly relevant for fruit industries in North America.

1. The development of new cultivars within a range of fruit types. Examples include new plum cultivars with longer storage potential and less susceptibility to chilling injuries. For apples, the huge impact that Honeycrisp has had on grower profitability has increased awareness of how consumers will respond to apples with improved texture and flavor. Along with these trends there has been greater emphasis on licensed cultivars in order to protect market share; these include Cosmic Crisp in Washington, SnapDragon and RubyFrost in New York, and Evercrisp in Ohio. Honeycrisp has been widely used as a parent in breeding programs, and many of the storage disorder susceptibilities have been inherited by progeny.


2. Changes in planting designs, especially intensive plantings and rootstock for apples. Increased yields, while of more uniform appearance, can result in fruits with compromised keeping quality because of lower carbohydrate and mineral concentrations.


3. Increasing interest in organic fruit production is accompanied by a requirement for compatible storage technologies. Chemical control measures are being replaced with often highly sophisticated and sometimes risky postharvest storage technologies.


4. Adoption of preharvest plant growth regulators such as aminoethoxyvinylglycine (ReTain) and 1-methylcycopropene (1-MCP; Harvista) has occurred in fruit industries to control maturity and ripening. Use of these compounds has increased greatly, largely in response to the need to reduce harvest costs and to manage harvest with fewer pickers.


5. The development of new non-destructive technologies for assessment of fruit maturity and quality. Examples include the Delta Absorbance (DA) meter for chlorophyll measurements, and the F750 meter for dry matter concentration measurements.


6. 1-MCP has been widely adopted for postharvest treatment of apples, but less used for other fruit types because it can inhibit rather than delay ripening, resulting in undesirable effects on product quality. However, 1-MCP has come off patent and a number of new postharvest technologies for application such as sachets and incorporation of 1-MCP into films are becoming available.  Additionally, new niche applications for 1-MCP continue to be developed.


7. The recent banning of the antioxidant, diphenylamine, in Europe raises concerns about its future viability in North America. One alternative technology, dynamic controlled atmosphere (DCA) storage, in which oxygen concentrations in storages are kept close to the anaerobic compensation point, is an option that needs further exploration.


8. Physiological disorders can be affected positively or negatively by storage technologies. For example, superficial scald of apples is inhibited by 1-MCP, DPA, and DCA storage, while other disorders, especially carbon dioxide-related ones tend to be increased by 1-MCP. In addition, a number of emergent disorders in apple (skin wrinkling, leather blotch, stem end browning) appear to be more prevalent, with no clarity yet on their causes.


9. Regulations related to immigration and guest worker programs continue to evolve. The expectation is that acquiring the needed labor for a timely harvest will become more challenging. This threat has already lead to the development of new harvest and handling technologies that have the potential to negatively impact the quality of the harvested fruit. The impact of these new technologies needs to be assessed in order to improve their performance and to inform farmers of benefits and liabilities.

Research in this project will focus on each of these needs over the next five years.

Importance of the Work

The multistate project described here is focused on fruit, reflecting the continued investment in postharvest issues related to fruit by the Agricultural Experiment Stations. The project objectives address a range of postharvest issues of fruits throughout the US as well as Canada.  Previous (NE103, NE1018, NE1036) and current (NE1336) versions of this project have made major contributions to the fresh fruit industry.  These include industry adoption of innovative applied methods developed by the group, and basic research on postharvest problems such as superficial scald, and bitter pit in pome fruits, and chilling injury (CI) in pome and stone fruits. The efforts of this project have led to more effective control measures and new knowledge of the genetic and biochemical causes of the disorders.  Other environmental impacts during fruit growth, especially elevated solar irradiation, are major contributors to annual postharvest losses in major US fruit production regions.  By necessity, our collective work continues to assess metabolic bases of these losses and identify novel solutions mitigating them in a changing regulatory environment such as sorting to improve storage consistency or remove high risk fruit.  Nonchemical and reduced risk chemical methods of preventing losses have been studied/developed as a way to extend storage life of highly perishable fruits such as berries.  Over the past five years, members of NE1336 have conducted extensive research on postharvest nutritional quality of many types of fruits to identify and quantify antioxidative constituents beneficial to human health, and to determine how the content and composition of these phytonutrients are influenced by cultivar and storage methods.  Studies on apples have continued to be a major focus, with an emphasis on newly emerging problems such as browning disorders and CI, which cause major losses for producers.  1-methylcyclopropene (1-MCP), an ethylene action and ripening inhibitor developed by members of this project, has been adopted as a common commercial means to control ripening and maintain quality in storage of apple and continues to be a critical area of research for NE1336.  As 1-MCP moves off patent, new applications of value to varied commercial interests are being assessed and uses with fruits other than apple are gaining a renewed interest.

Consumers prefer newer apple cultivars and are willing to pay more for them compared with older cultivars (Yue and Tong, 2011). ‘Honeycrisp’ apple, a relatively new cultivar with high consumer demand, has been widely planted in the U.S., and a number of physiological disorders have been identified through the activities of the NE1336 that raise challenges for continued expansion. As this cultivar is widely used in breeding programs across the United States, postharvest testing of Honeycrisp and its progeny, from different orchards and regions, will provide useful information to growers and shippers, especially those forming marketing cooperatives.  Information on problems with both older, established cultivars and replacement cultivars in regional growing areas has become increasingly important as locally grown and food safety issues have made consumers more interested in regionally produced fruit.

Technical Feasibility of the Research and Advantages for Doing the Work as a Multistate Effort

As a group, researchers in the current project (NE1336) actively collaborate to find solutions to problems faced by the fruit industry.  The researchers in this project have skillsets that span a number of scientific fields (e.g., pathology, engineering, nutrition, physiology, biochemistry and molecular biology) and have an established track record for collaboration on projects across North America and continue to recruit new collaborators.  The project actively develops solutions for rapid implementation to maintain industry profitability, while supporting the applied research with a strong basic program that seeks to understand fruit physiology and biochemistry, particularly in relation to responses to genetic differences among cultivars, and responses of fruits to technologies such as 1-MCP and CA storage regimes. The genetic underpinnings of the biochemical mechanisms involved in the induction of storage disorders and fruit quality are being elucidated, often in association with grants based on research that was originally carried out under the auspices of this project.  One example is a USDA NIFA Specialty Crops Project that is exploring the genomics and metabolomics of several physiological disorders. Future combined efforts hold the promise of finding the causes of browning disorders such as bitter pit, chilling injuries, CO₂ injury, and emergent physiological disorders. Increasing consumer appeal of U.S. fruit through improvement of texture, flavor, and aroma, and preventing losses for growers can best be approached by a broad array of sensory, physiological, biochemical, and molecular genetic techniques. 

Storage protocols for fruits are cultivar- and often region-specific, and must be optimized to reduce postharvest losses. Further, many storage disorders are impacted by local growing conditions and the cultural activities of the grower. The broad geographical distribution of the team in this project provides a unique opportunity where responses of cultivars to a wide range of growing conditions can be studied and the difficulties posed by the intrinsic variability of a fruit crop can be overcome.  To this end, several institutions have installed equivalent facilities, such as those for controlled atmosphere (CA) storage, enabling parallel investigations across regions. An example is the investigation of the sensitivity of the apple cultivar Honeycrisp to the elevated CO₂ concentrations encountered in CA storage. Some NE1336 members have focused on the impact of the rate of establishment of the desired atmosphere, others have evaluated chemical and cultural techniques for controlling the sensitivity of the fruit, and others have evaluated the role played by environment in fruit sensitivity to the CA atmosphere. Through combined effort, the NE1336 membership work as a research and extension team to solve industry problems and to provide rapid dissemination of research results that would not occur without the organization of a multistate project. This has become especially important as the interest in locally grown fruits demands a mobilization of knowledge and adaptation to the varied resources of small to large farms. As no individual state has the expertise and resources required to address all aspects and issues of fruit quality, the multistate project can combine their respective strengths for a synergistic and coordinated effort to investigate postharvest issues and problems, and provide much needed recommendations and solutions to the fresh fruit industry, both regionally and nationally.

Integration of sensory testing into postharvest research has been challenging, as physical measurements of quality do not always predict consumer preferences. An exciting addition to the project is the sensory research to be carried out by Dr. Dando (Cornell University).  Cost effective sensory analyses are difficult, and most postharvest research data are based on physical measurement such as texture, soluble solids, and acidity. Dando will develop a sensory framework for use by various stations involved in the project across North America.  Initially this research will focus on Honeycrisp apple, but will expand to other cultivars as necessary.

 Impact

The accomplishments of the NE1336 project include extensive evaluation of fruit cultivars and development or modification of methodologies to best enhance storage life, quality, and flavor and the elucidation of mechanisms involved in flavor and storage disorder development in fruits. Another excellent example of impact resulting from our continued collaboration of at least six research units participating in NE1336 to establish the best postharvest practices for the Honeycrisp apple in various regions of the U.S. and Canada. The NE1336 program has generated key information that has at least provided solutions to storage of this cultivar, including the development of CA storage regimes. Successful transfer of information to researchers and industries has been done via peer-reviewed publications, grower meetings and trade publications, and a website.  Most members of this project have strong extension/outreach programs associated with their research and they have been successful at changing the behavior of the fruit industries. The North American apple industry, for instance, has directly and demonstrably benefitted from the research and extension efforts of the NE1336 and now uniformly employs a protocol for suppressing chilling injury in Honeycrisp.

The proposed new project will make similar valuable contributions, continuing to develop and improve methods and technologies for evaluation, maintenance, and genetic enhancement of postharvest quality of fresh fruits. The primary goals of our new research project are to increase competitiveness for domestic fruit production and preserve 'fresh-picked' sensory and nutritional quality, which in turn will increase the availability and consumption of locally grown and highly perishable fruit. To meet these goals, we make better use of existing storage technologies, and develop new, safer technologies requiring minimal use of chemicals. We do not have an economist formally involved in the project because of commitment to other projects, but they (e.g., Brad Rickard, NY) are willing to contribute as needed. The overall impact of this project will be to improve the long-range health of the American populace via greater consumption of fresh fruits, and to increase profitability of organic and convention operations at all levels of scale.

One of the most valuable aspects of this Multistate Project is the connection among members conducting basic research and those involved in applied science.  Fundamental information relating to fruit physiology, molecular biology, and biochemistry is developed by some members of the Technical Committee and then used by other members to guide their more applied research. Examples of such collaborations include work on ethylene action and ripening, quality loss, biosynthesis of aroma and flavor compounds, and storage disorder development. Conversely, the applied research identifies and defines problems in a way that helps refine inquiry at the fundamental level. Techniques and methods developed by NE1336 members have led to advances in maintenance of fruit quality and consistency, reduction in pesticide use, and practices that are easily tailored for regional and small-scale fruit production systems.  Introduction of new fruits through postharvest manipulation has added more consumer choices. Annual reports are available on the NIMSS project website (http://nimss.umd.edu/homepages/home.cfm?trackID=10057), and publications resulting from this project for 2012-2017 are listed in Appendix B.