NE1036: Postharvest Biology of Fruits
(Multistate Research Project)
Status: Inactive/Terminating
NE1036: Postharvest Biology of Fruits
Duration: 10/01/2008 to 09/30/2013
Administrative Advisor(s):
NIFA Reps:
Non-Technical Summary
Statement of Issues and Justification
The Need: Consumption of fruit contributes substantially to human health, and increased fruit consumption is suggested as one means to help curb the alarming rise in obesity and diabetes in the U.S. American markets offer an array of moderately priced fruits of apparent good quality, the result of decades of effort by fruit breeders and postharvest specialists, yet daily consumption continues to fall far short of the recommended 3 to 5 servings. Despite abundance and availability, consumers limit fruit purchases, their foremost complaints being insufficient quality and lack of flavor. Fruit producers often market fruit from cultivars with marginal quality and flavor to maintain market share, or switch to new cultivars with perceived increased value, but for which several years of research are needed to best maintain postharvest quality and shelf life. The key to increasing consumption of fresh fruits, and for maintaining grower income, viable U.S. fruit production, and export opportunities, lies in providing fruit with superior flavor and long shelf life that are also perceived as healthy, both in terms of nutrition and minimal risks from agrichemicals or pathogens. Fresh fruit industries continue to rely heavily on postharvest chemicals to control microbial decay, insects, and physiological disorders during storage. Moreover, some fungal pathogens on stored apples and other fruits produce cancer-causing mycotoxins, thus increasing the need for disease control. While advances have been made in nontoxic alternatives or sustainable systems, changes in the types and amounts of chemicals used have created a need to modify storage technologies. New approaches are needed to minimize losses of fruit during storage and transport, and thereby maintain global market share for domestic producers. A better understanding of relationships between postharvest physiology of fruits and their susceptibility to decay, disorders, and insects is essential for developing improved control measures and reducing chemical use. Adoption of non-apple production by small acreage growers or by tree fruit growers who wish to expand crop diversity have increased over the last five years. Cultivation of many small fruits and vegetable fruits can easily be adapted to fit organic production or extended harvest (i.e., tunnel and plasticulture) systems, but cultivars and genotypes suitable to these systems often differ from those used in traditional systems. Small fruits also differ from many tree fruits in length and type of storage, ethylene sensitivity, and types of disorders. Hence, postharvest technologies must be developed or modified to extend storage life and maintain quality and safety in small, organically produced, and extended season fruits. Importance of the Work: Previous (NE103) and current (NE1018) versions of this project have made considerable contributions to the fresh fruit industry. These include adoption by the industry of innovative applied methods developed by the group, and basic research on postharvest problems such as superficial scald in pome fruits, which has led to more effective control measures and knowledge of the genetic and biochemical causes of the disorder. The discovery and commercialization of 1-methylcyclopropene (1-MCP) as a means of controlling fruit ripening, maintaining fruit quality in storage, and reducing storage disorders has developed into a critical area of research for this project. 1-MCP was approved for food use in July 2002 and is currently used commercially on apples in several states. It has very low toxicity and negligible residues, and is effective at low concentrations. Over the past five years, members of NE1018 have conducted extensive research on postharvest quality of apples treated with 1-MCP, and the concerted efforts of NE1018 have been instrumental in providing information to the fresh fruit industry that was essential for successful postharvest utilization of the technology. With new formulations of 1-MCP, preharvest sprays in orchards are now possible. The effects of these sprays on subsequent apple drop, apple quality, decay susceptibility, and shelf life are not known, and our new multistate project will conduct the research required to evaluate, optimize, and implement this new technology. Technical Feasibility and Value of a Multistate Project: As new fruit crops and cultivars are introduced and production practices are modified, there are continuously emerging postharvest challenges and needs for development of new storage and quality methodologies. Storage protocols for temperate fruits are cultivar- and often region-specific, and must be optimized to reduce postharvest losses. The broad geographical distribution of the team in this project provides a unique situation where responses of cultivars to a wide range of growing conditions can be studied. New apple cultivars such as Honeycrisp have been widely planted in the U.S. and a number of physiological and pathological disorders limit continued expansion and threaten viability of the industry. Information on problems with both older, established and replacement cultivars in regional growing areas has become increasingly important as fossil fuels and food safety issues have made consumers more interested in regionally produced fruit. At least six research stations participating in NE1018 are currently collaborating to establish the best postharvest practices for the prized and profitable Honeycrisp apple in various regions of the U.S. and Canada. Plans for collaboration in the new multistate project include application of neural network analysis, using existing data from orchards in many locations to determine how orchard management regimes influence the incidence of storage disorders in Honeycrisp as well as other apple and pear cultivars. A group of NE1018 researchers is also on the cusp of elucidating the genetic and biochemical mechanisms involved in the induction of superficial scald, and future combined efforts hold the promise of developing new scald-resistant cultivars that do not require the chemical drench currently used to control the costly disorder. Increasing consumer appeal of U.S. fruit through improvement of texture, flavor, and aroma can best be approached by a broad array of sensory, physiological, biochemical, and molecular genetic techniques. No individual state has the expertise and resources required to address all aspects and issues of fruit quality, but in a multistate project their respective strengths can be synergistically applied in a coordinated effort to solve problems with quality and flavor. A multistate project provides a team approach, rich in ideas and expertise, and therefore is best suited to investigate postharvest issues and problems, and provide much needed recommendations and solutions to the fresh fruit industry, both regionally and nationally. Impact: The products of the NE1018 project have included extensive evaluation of apple cultivars and development or alteration of methodologies to best enhance storage life, quality, and flavor; the development of effective protocols that can be used by the industry for controlled atmosphere/low oxygen storage; and the elucidation of mechanisms involved in flavor and storage disorder development in fruits. 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 encourage more fruit consumption for improved human health. To meet these goals, we will evaluate the storage potential of new cultivars, make better use of existing storage technologies, and develop new, safer technologies requiring minimal use of chemicals. Underpinning this research, we have a group investigating the metabolism of ripening and the biological causes of physiological disorders. Our research emphasis has shifted somewhat, with greater focus on the effects of postharvest handling on fruit nutritional and flavor quality because of their importance to consumers. Specialist skills within this multistate project will foster collaborative activity among regions, enabling broader and more rapid advances in postharvest research. 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 large-scale national as well as small-scale, local and organic fruit production.
Related, Current and Previous Work
NE1018 has been prolific in cooperative research efforts, especially with apples, and has made many significant contributions to postharvest fruit research. Applied research has centered on germplasm evaluation, including susceptibility to and identification and causes of storage disorders, decay incidence and organisms, and postharvest quality loss. Extension outreach for growers and packinghouses on issues such as disease control and modification of sanitation, storage, and handling protocols is an important function of the group. Fundamental research on the genetic and biochemical mechanisms of texture loss, volatile aroma/flavor production, storage disorder development, and ethylene production, perception, and action is shared with collaborators to foster multi-systems approaches within the group. Applied and basic research on antioxidants and health benefits of fruits brings together horticulture, nutrition, and medicine. One of the most valuable aspects of this Multistate Project is collaboration between members conducting basic research and those involved in applied science. Fundamental information relating to various aspects of 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 ripening, softening, aroma synthesis, fungal decay, scald, storage, and ethylene action. Techniques and methods developed by NE1018 members have led to advances in maintainence of fruit quality and consistency, reduction in pesticide use, and practices that are easily tailored for regional fruit production systems. Annual reports are available on the NIMSS project website (http://lgu.umd.edu/lgu_v2/homepages/home.cfm?trackID=3994), and publications resulting from this project for 2003-2008 are listed in Appendix B. Both NE1018 and the previous project (NE103) investigated relationships between apple storage quality and preharvest factors known to markedly affect postharvest performance (Bramlage, 1993; Bramlage and Weis, 2004). Studies on the mineral nutrition of apple fruit improved our understanding of mechanisms of calcium (Ca) action (Burmeister and Dilley, 1993; Picchioni et al., 1998; Sams and Conway, 2003; Whitaker et al., 1997) and developed prophylactic treatments of fruit, both pre- and post-harvest (Conway et al., 1994; Rosenberger et al., 2004c). Research on the effect of plant growth regulators such as aminoethoxyvinylglycine (AVG; ReTain) and ethephon, as well as other harvest management factors has continued (Clayton et al., 2003; Moran, 2006a,b; Rosenberger, 2006; Stover et al., 2003; Wang and Dilley, 2001; Wargo et al., 2003, 2004). Utilization of new technologies and cultural tools is often limited by highly variable responses of the stored fruit. For instance, fruit cultivars differ markedly in their response to, and tolerance of, low O2 (Beaudry, 2000), high CO2 (Burmeister and Dilley, 1995; Fernandez-Trujillo et al., 2001; Watkins, 2000; Watkins et al., 1997), and other postharvest treatments (Fan et al., 1999a,b; Watkins et al., 2000). Responses of cultivars to many postharvest treatments are affected by growing environment (Lau et al., 1998; Tong et al., 2003). Cultivars also vary widely in susceptibility to storage disorders such as superficial scald, soft scald, low temperature breakdown and senescent breakdown (Barden and Greene, 1997; Watkins et al., 2004; Whitaker et al., 2000; Wolk et al., 1998). Development of new cultivars for North American fruit industries has become key to economic success. Information on storability of apples and many other fruits has been produced by NE103 and NE1018 (Agar et al., 1999; Amodio et al., 2007; Clayton et al., 2003; Cliff et al., 1998; Defilippi et al., 2006; El-Shiekh et al., 2002; Grant et al., 1996; Guevara et al., 2006; Khanizadeh et al., 2006a-c, 2007a; Kupferman, 2002a,b,c,d; Kupferman and Gutzwiler, 2002; Lau and Lane, 1998; Luengwilai et al., 2007; Palou et al., 2003; Pelayo-Zaldivar et al., 2005, 2007; Reed, 2002; Shin et al., 2005, 2007; Volz et al., 1998; Watkins et al., 2003). A multi-state study involving quality evaluation of apples from new genetic selections, in which NE1018 collaborated with NE183, was completed in 2005. New cultivars developed from these apple selection trials were evaluated for postharvest requirements and 1-MCP compatibility (Bai et al., 2005). After two seasons of screening the NE183 selections, and in response to extensive plantings across North America, the focus was narrowed to a single cultivar, Honeycrisp. This apple has unique flavor and texture characteristics and is highly profitable, but it is also very susceptible to physiological disorders including soggy breakdown, soft scald, and bitter pit. NE1018 research has thus far identified risk factors for these disorders (Robinson and Watkins, 2003; Tong et al., 2003; Wargo and Watkins, 2003, 2004; Watkins et al., 2003a,b, 2005; Weis, 2003), and developed initial strategies to minimize fruit losses and thereby prevent erosion of industry confidence in the cultivar (DeLong et al., 2006; Rosenberger et al., 2003, 2004c; Watkins et al., 2004). Small fruits and vine crops, such as blackberry, raspberry, strawberry, blueberry, grape, and kiwifruit, have become more widely planted across the U.S. These fruits have a high cash value as both U-pick and shipping acreages, provide an additional income source to apple producers, and offer a viable income for small acreage growers. Many of them are easily grown with few or no pesticides and are thus good candidates for transition to organic production systems (Amodio et al., 2007). An increasing number of small fruit growers are interested in use of extended season systems, such as row covers and plastic tunnels, to add value and quality to their crops. New types of blackberries have been developed (primocane-fruiting) that are suitable for these systems (Clark et al., 2005), but fruit firmness is poor and needs to be evaluated in new releases. Postharvest studies on numerous other small fruit genotypes are scant or non-existent. The apple industry's successful use of SmartFresh technology, based on 1-methylcyclopropane (1-MCP), an ethylene action and ripening inhibitor, was made possible through the coordinated research of members of NE1018. Collaboration of project participants on uses of 1-MCP led to a national transfer technology award in 2006. Overviews of 1-MCP use on horticultural crops have been published by our members (Blankenship and Dole, 2003; Mattheis, 2008; Prange and DeLong, 2003; Watkins, 2002, 2006, 2007, 2008) and our findings have been disseminated to horticulturists and plant physiologists through national and international meetings. Of the temperate fruits, apple, pear, apricot, peach, plum, strawberry, and persimmon respond to 1-MCP applications to various extents (Watkins, 2006, 2008), and more research on these and other fruit crops is required to develop further protocols for commercial use. 1-MCP is generally effective for delaying ripening of apples, with the response saturating at about 1 mL L-1 for most cultivars (Fan et al., 1999a; Rupasinghe et al., 2000b), but some require higher concentrations for full response (Watkins et al., 2000). The treatment duration needed to provide maximal response is dependent on temperature, and cultivars may differ in the minimum time needed to gain maximal benefit (DeEll et al., 2002). 1-MCP has been shown to reduce senescent scald, superficial scald, respiration, softening, ethylene production, and aroma volatile synthesis in apples (Bai et al., 2005; DeEll et al., 2002, 2005a,b, 2007; Fan and Mattheis, 1999a; Fan et al., 1999a,b; Lurie et al., 2002; Moran, 2006a-c; Moran and McManus, 2004, 2005; Rupasinghe et al., 2000a; 2001). The level and duration of response are often cultivar-specific, and harvest maturity is an important factor (Argenta et al., 2005; Watkins et al., 2000). Members of NE1018 have made good progress in determining how 1-MCP affects fruit physiology and metabolism, particularly at the level of gene expression and enzyme activity. Studies have included effects on metabolism of flavor compounds and antioxidants (Dandekar et al., 2004; Defilippi et al., 2004; MacLean et al., 2006, 2007), synthesis of esters and other aroma volatiles (Defilippi et al., 2005a,b; Ferenczi et al., 2006), ethylene perception and biosynthesis (Dandekar et al., 2004; Defilippi et al., 2005a; Tsantili et al., 2007), and, in relation to superficial scald, synthesis of a-farnesene (Gapper et al., 2006; Lurie et al., 2005; Pechous and Whitaker, 2004; Pechous et al., 2005; Tsantili et al., 2007), and activity of antioxidative enzymes (Arquiza et al., 2005). Other recent studies have focused on 1-MCP treatment as an alternative to CA or to combat disorders in specific cultivars, and the effects of 1-MCP in combination with CA (Bai et al., 2005; DeEll et al., 2005a,b, 2007; Moran and McManus, 2005; Moran, 2006). Many of the 1-MCP studies were done under ideal experimental conditions but the effects of maturity, delays between harvest and treatment, and other postharvest factors continue to be investigated (Argenta et al., 2005; Mir et al., 2001; Watkins, 2008; Watkins and Nock, 2005). Some instances of a negative influence on quality have been noted in apple (Watkins, 2007, 2008; Mattheis, 2008). Although the occurrence of damage has been variable, enhanced sensitivity of some cultivars to CO2 injury and flesh browning resulting from1-MCP treatment is of serious concern (DeEll et al., 2001, 2005a,b, 2007; Fawbush et al., 2008; Watkins, 2008). The NE1018 group has made major contributions to the study of superficial scald control for apples and pears. Low O2 CA storage has been extensively studied as a non-chemical means to control scald, including a collaborative project among stations (Lau et al., 1998). While results from our studies indicate that growing region and climatic variation markedly influence scald development and intolerance to low O2 atmosphere, chlorophyll fluorescence monitoring in combination with modulated low O2 can be used to establish threshold O2 levels that prevent scald and avoid injury (DeLong et al., 2007; Prange et al., 2002; 2007). A strong correlation was shown between ethylene-induced up-regulation of a-farnesene synthase (AFS1) gene expression and subsequent accumulation and oxidation of a-farnesene in air-stored apples and pears (Pechous and Whitaker, 2004; Lurie et al., 2005; Pechous et al., 2005; Gapper et al., 2006; Tsantili et al., 2007). Genes encoding enzymes in the a-farnesene biosynthetic pathway were cloned and characterized (Rupasinghe et al., 2001; Pechous and Whitaker, 2002, 2004; Lurie et al., 2005; Pechous et al., 2005; Gapper et al., 2006; Tsantili et al., 2007). Cultivar and fruit surface (blushed versus unblushed skin) differences in scald susceptibility cannot be fully explained by a-farnesene production, and may also reflect differences in antioxidative systems (Fernández-Trujillo et al., 2003; Kochhar et al., 2003; Arquiza et al., 2005; Pechous et al., 2005; Tsantili et al., 2007). It was shown by Tsantili et al. (2007) that failure of 1-MCP to completely control scald in some cultivars is related to release from inhibition of ethylene perception. The two most common pathogens causing postharvest decays of fruit crops are Botrytis cinerea and Penicillium expansum. Control with benzimidazole fungicides has been compromised by development of pathogen resistance, so the newer fungicides fludioxonil and pyrimethanil were extensively evaluated over the past five years (Rosenberger et al., 2004a,b; 2005a-e; 2007a-d; 2008), and were recently registered to control these diseases on pome fruits. Pristine fungicide (pyraclostrobin + boscolid) was shown to suppress postharvest decays when applied to fruit prior to harvest (Rosenberger et al., 2007d, 2008a-c). Alternative, non-fungicidal approaches evaluated for controlling postharvest decays have included biological controls, heat treatments, ozone, adjusted N2, Ca or B levels, or volatiles (Zhou et al., 2000; 2001; Palou et al., 2001, 2003; Okull et al, 2006; Simpson et al, 2003; Song et al, 1998; Wszelaki and Mitcham 2003), or combinations of these treatments (Conway et al., 2004, 2005; Wszelaki and Mitcham, 2003). Rosenberger (2001) reported that P. expansum recycles on field bins and its spores are present at high concentrations in packinghouse air. Proven sanitation measures involve the use of reducing agents that either can injure fruit or are incompatible with antioxidants such as DPA. Continued research is needed to identify cost-effective sequences for application of sanitizers, fungicides, and other postharvest treatments that are safe for the crop, applicators, and consumers. Insects continue to play a role in postharvest quality and storage of fruits and NE1018 has worked on chemical alternatives, or more environmentally friendly chemicals, for control. Some of the alternative strategies that have been explored for postharvest insect control include natural fumigants, surfactants, heat treatments with water, air or radio frequency energy, and controlled atmosphere treatments, but additional work on fruit tolerance is needed (Simpson et al., 2003; Tipping et al., 2003). Postharvest heat treatments using radio frequency energy have been developed for walnut (Wang et al., 2001; Mitcham et al., 2004) and hot water treatments developed for sweet cherry (Feng et al., 2004). Phytochemicals encompass a host of nutritive and non-nutrative compounds found in plants that offer protective effects against chronic and degenerative diseases (Heinonen et al., 1998; Record et al., 2001). Important groups include phenolics, nitrogenous compounds, ascorbic acid plus glutathione, tocopherols, and carotenoids. Many of the phytochemicals present in fruits and vegetables exhibit anticarcinogenic and antimutagenic activity (Weisburger, 1999). Khanizadeh et al. (2007b) reported that apples vary in phenolic composition and antioxidant activity among genotypes. Research has begun on the antioxidant and anti-proliferation activities of strawberries (Meyers et al., 2003) and effects of postharvest treatments on these activities (Shin et al., 2007, 2008). McLean et al. (2003, 2006) reported effects of 1-MCP on antioxidants in apples. Jacob et al. (2003) showed that sweet cherry consumption had anti-inflamatory and anti-gout effects in humans. Watermelon may improve cardiovascular health by inducing arginine and stimulating nitric oxide production (Wu et al., 2007; Collins et al., 2007). Eggplant fruit contain high levels of antioxidant caffeic acid conjugates (Stommel and Whitaker, 2003; Whitaker and Stommel, 2003) that lower blood pressure and serum cholesterol. There is great interest in fruits and vegetables as potential alleviators of chronic diseases in medical and nutritional fields. Further research is needed on phytochemical composition among fruit, and the influence of production, germplasm, storage conditions, and storage treatments. Consumer sensory perceptions differ among fruits and must be defined to improve appeal of fruit for initial and repeat consumption. Consumer and sensory panels have been used to describe how people react to apples of varied quality (Abbott et al., 2004; Allan-Wojtas et al., 2003; Andani et al., 2001; Boulton, 1997). Using information from these studies, researchers are determining how consumers evaluate edible and visual quality of apples. Texture is a very important quality component and is dependent on cultivar, orchard conditions, storage temperature, and ethylene (DeEll et al., 2001; Johnston et al., 2002; Johnson, 2000). Genetic variability can be exploited to study the molecular and physiological mechanisms controlling maintenance of fruit texture (Tong et al., 1999), and manipulation of pre- and post-harvest conditions can be used to improve apple eating quality. In strawberry, fruit flavor can be strongly affected by harvest date, cultivar, and CO2 storage (Fernandez-Trujillo et al., 1999; Zhang and Watkins, 2005; Pelayo-Zaldivar et al., 2005, 2007). Peach fruit consumption can be increased through prevention of chilling injury, which causes internal breakdown, mealiness, and loss of flavor (Brummel et al, 2004; Peace, 2006; Peace and Crisosto, 2006). Ongoing work on molecular aspects of softening and aroma development will greatly advance our knowledge of the genetic and biochemical mechanisms, and ultimately yield new techniques for improving and maintaining flavor and firmness. NE1018 researchers have also examined factors that influence a fruits ability to resist infection by postharvest pathogens. Research on the polygalacturonase inhibitor protein (PGIP) in fruit by labs in Beltsville and Davis may lead to reductions in the use of fungicidal chemicals while reducing fruit decay (Dhallewin et al., 2004; Powell et al., 2000; Yao et al., 1999). Continuing work with PGIP is designed to understand details of its contribution to fruit resistance to fungi. Work on apples indicates that growth of different fungi on fruit may cause tissue pH changes that either support or repress the growth of the food-bourne human pathogen Listeria monocytogenes on the fruit. This study could pave the way to biological methods for control of this and other human pathogens (Chardonnet et al., 2002). Effects of other fungi on tissue pH may also influence the ability of fruit fungal pathogens to macerate host tissues (Prusky et al., 2004). Ethylene production is critically important to maturation and ripening processes in climacteric fruit, whether or not the fruit are stored. Molecular genetic down-regulation of ACC synthase and ACC oxidase gene expression in apples suppresses fruit softening and, along with 1-MCP treatment of wild-type fruit, has provided experimental material useful in studies of metabolic processes controlled by ethylene during ripening (Dandekar et al., 2004; Defilippi et al., 2004, 2005a,b; Hrazdina et al., 2003). Both normal and stress-induced senescence in fruit tissues involve loss of membrane structure and function. Genes encoding phospholipase D± isozymes and lipoxygenase, which catalyze membrane degradation during senescence, have been cloned (Whitaker et al., 2001; Whitaker and Lester, 2006) and used in antisense or RNAi silencing constructs in transgenic tomato and melon plants. Reduced fruit water loss and extended storage life are foreseeable outcomes of this fundamental research.
Objectives
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Determine genetic and biochemical mechanisms governing loss or retention of fruit quality after harvest.
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Develop or adapt postharvest strategies and technologies to improve quality and market competitiveness of emerging production systems, including organic, local, and small-scale.
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Develop technologies and practices that optimize market returns and promote increased consumption of health-beneficial fruits through preservation or improvement of fruit quality attributes.
Methods
Objective 1: We will determine genetic and biochemical mechanisms governing loss or retention of fruit quality after harvest. Understanding of the basic biology that underlies development of physiological and pathological disorders in fruits continues to be an important aspect of this project. A number of disorders are affected either positively or negatively by ethylene, and therefore this research is critical to continued adoption of 1-MCP-based technologies as well as providing increased understanding of the role of ethylene in sensitivity of fruit to storage disorders. The research under this objective is closely integrated with the applied technologies described in Objective 3, and will focus on the following disorders: 1a. Superficial scald. We propose to extend investigations on scald with several approaches. Because scald development appears to be linked to active oxygen species (AOS) generation in apple skin and AOS may perturb ethylene perception and subsequent responses, spin-trapping will be used to characterize the specific organic O2 species that accumulate [WA-P]. Metabolism linked with scald inception and development will be investigated [USDA-WA] and new scald-linked compounds will be identified [USDA-WA, USDA-MD]. Treatments known to ameliorate scald will be employed as controls in comparative analyses. Molecular, biochemical, and physiological mechanisms involved in superficial scald development in apple and pear fruits will be studied [USDA-MD, NY-I, NY-G, MI]. Transformation of scald-susceptible Granny Smith apple with RNAi silencing constructs of the ±-farnesene synthase gene, AFS1, will definitively test the role of ±-farnesene oxidation products in scald induction, and AFS1 promoter function will be analyzed to determine how the gene is up-regulated by ethylene and low temperature [USDA-MD, NY-G]. A collaborative study will determine if ±-farnesene synthesis and oxidation are linked with scald that occurs in CA-grown but not in WA-grown Bartlett pears [USDA-MD, CA, USDA-WA]. Proteomic technology will be used to investigate the biochemical mechanisms of scald. Investigating the effects of treatment with DPA and 1-MCP on apple fruit to identify up and down-regulated proteins which may be responsible for scald development and/or resistance [NS]. Promising strategies for controlling superficial scald on apples will be integrated with traditional protocols and subjected to a system evaluation. The criteria for evaluation will be ease of transition, profitability, and sustainability of the strategies [WA, USDA-WA]. Optimization of ULO storage for control of storage scald utilizing chlorophyll fluorescence to achieve the lowest possible O2 concentration will continue [NS]. 1b. Flesh browning disorders. Several cultivars are susceptible to flesh browning disorders. The ones of importance to our industries include internal CO2 injuries such as Braeburn browning disorder (BBD), soft scald, and diffuse flesh browning. The incidence of these disorder types can be increased by 1-MCP (Mattheis et al., unpublished; Watkins, 2006, 2007, 2008; Zanella et al., 2005), but in contrast to scald, little is known about the metabolic basis of disorder development. In Objective 3, we will develop maturity, storage and handling factors that will mitigate disorder development; in this objective, our efforts will be focused on understanding the metabolic processes involved in BBD and flesh browning. Primary focus will be on Honeycrisp [USDA-WA] and Empire [NY-I]. Our approach will be to study metabolic changes (sugars, acids, antioxidative systems, phenolics) using GC, GC-MS and other analytical methods, as well as genomics methodologies. 1c. Bitter pit. This calcium deficiency disorder that occurs in apples and pears (Ferguson and Watkins, 1989) has been difficult to ameliorate across growing areas. The molecular and physiological mechanisms underlying this disorder will be studied in apple [CA]. Tomato fruit will also be used as a model system to investigate calcium/growth regulator interactions involved in development of the calcium deficiency disorder blossom end rot. 1d. Pathological disorders. Patulin, a carcinogenic fungal secondary metabolite in apple products, poses a major health threat to consumers. Control of postharvest toxin levels in apples by use of ambient lighting conditions will be explored [NY-I]. Light requirements, including spectral distribution and duration of exposure, needed to reduce patulin production in apples infected with P. expansum will be characterized, and a practical method to minimize patulin accumulation during apple storage will be developed. Expression patterns of key enzymes involved in patulin production as influenced by light and temperature will be determined. Other major components of Objective 1 involving determination of genetic and biochemical mechanisms governing loss or retention of fruit quality after harvest are as follows: 1e. Ripening initiation. Molecular and biochemical mechanisms regulating development of capacity to ripen in pear fruit will be studied [CA]. Ripening processes of watermelon, such as changes across tissues in pH, sugars, and lycopene synthesis, will be followed to determine the site of ripening initiation [OK]. 1f. Texture. Studies of fruit cell wall metabolism in relationship to tissue softening and the generation of active oligosaccharide signals (PDOs) will use tomatoes with genetically altered production of wall-metabolizing enzymes, biochemical and genomic searches for previously undescribed fruit enzymes, and extraction and characterization of endogenous PDOs and testing of their potential biological activities on fruit pericarp explants [CA]. Complementary studies on genetic and biochemical factors involved in tomato fruit softening will be conducted using the recently-characterized, unique DFD (delayed fruit deterioration) mutant [NY-I]. Genetic control of apple texture (crispness) will be studied by identifying genes that are expressed in freshly harvested apple fruit but not in stored fruit using a PCR-based technique [MN, USDA-WA]. The expression of these genes in different apple cultivars will also be determined. The function of such genes will be determined by silencing or increasing their expression in apple fruit, followed by characterization of fruit phenotype. New cultivars or lines derived from this work will be evaluated for overall quality by other members of the Technical Committee. 1g. Flavor/Aroma generation. Work on apple fruit ester synthesis will continue with the focus on AAT genes and enzyme activity [WA-P, MI]. Studies examining the reasons that flavor-life of fruits is shorter than their appearance-life will focus on the relationships between sugar, acid, phenolic, and volatile components and overall sensory perception in a number of fruits; and ester synthetic pathway activity and ethylene responses in apple fruit lines that have been engineered to have reduced ethylene biosynthetic capacity [CA]. 1h. Senescence- and ripening-related gene expression. The rates of ripening, softening and senescence in tomato and melon fruits from plants transformed with RNAi silencing constructs of phospholipase D± (PLD±) and lipoxygenase (LOX) genes will be studied. Ripening and senescence characteristics will be assessed in whole fruit and in fresh-cut fruit slices [USDA-MD, USDA-TX, CA]. Studies on the biochemical responses of apple fruit to elevated CO2 will continue [NY-I, ON]. The role of oxidative stress and antioxidant metabolism in maintaining fruit quality will be studied [NS] Objective 2: We will develop or adapt postharvest strategies and technologies to improve quality and market competitiveness of emerging production systems, including organic, local, and small-scale. 2a. New cultivar development. Honeycrisp continues to be planted widely throughout North America, with largest plantings occurring in WA.We will continue to focus collaborative efforts on Honeycrisp apples to investigate the relationships among preharvest treatments, maturity, storage temperature, and postharvest treatments on the incidence of disorders [MA, ME, MI, MN, NS, NY-I, WA]. Of special need is the development of CA-based strategies for Honeycrisp as research to date indicates that fruit from certain regions, e.g. NS, store well under CA conditions, whereas fruit from other regions develop unacceptable levels of disorders. A website will be developed that can be easily updated to incorporate the varied results previously found from locations, and offer management methods tailored to production region [MA, ME, MI, MN, NS, NY-I]. Novel data mining concepts, such as Neural Network Analysis, will be employed with data obtained by NE1018 participants to identify pre- and post-harvest factors associated with the occurrence of disorders in Honeycrisp apple fruit [NS]. Postharvest decay problems in Honeycrisp will be addressed using several approaches. Identity of the pathogens causing decays in will be determined by isolating pathogens from samples provided by commercial growers in various states [ME, MI, MN, NY-G], and after pathogen identification participants will evaluate possible preharvest.factors contributing to decay. Botryosphaeria species often cause the most postharvest decay on Honeycrisp, and therefore factors and summer fungicides contributing to latent infections or fruitlet mummies will be evaluated. Effectiveness of field-applied fungicide strategies will be evaluated by determining pathogen populations on fruit using the paraquat method (Biggs, 1995) and observing intact fruit for decay incidence during storage [NY-G]. Postharvest decay development in Honeycrisp may also be related to sub-lethal heat stress in sun-exposed fruit during summer heat waves. Methods will be developed to induce heat damage on marked fruit in the field and then determine if heat-stressed Honeycrisp fruit show increased susceptibility to postharvest decays [NY-G]. 2b. Development of application protocols for small farms. In most fruit production areas in North America, and especially in the NE, small farms and integrated farm markets constitute an important component of the tree-fruit industrys production and sales. Application technologies for 1-MCP have thus far only been evaluated with large production and storage facilities in mind. There is a continuous need to serve the smaller production and retail facilities. Systems for 1-MCP application, such as refrigerated trailers and small cold rooms suitable for small farmers to use profitably, will be evaluated [MA, NC, ON]. Management strategies will be developed to minimize losses caused by 1-MCP-induced disorders in apples [NY, ON] for more effective use of the technology by small growers. Storage techniques will be developed for organic and small-scale producers to improve and extend the eating quality of local and high value apple varieties grown under organic, conventional, and integrated management. Research methods will focus on safe and effective techniques, such as ultra low O2 CA storage, that can be adapted by small-scale apple producers [ME, NS, USDA-MD, MD]. Postharvest handling practices for emerging fruit crops (non-apple) will be optimized for small-scale farmers [CA]. Cost-benefit analyses of these practices will be performed using economic models [MN, NY-I]. Organically approved fungicides (i.e., copper, sulfur, liquid lime-sulfur) that can be applied during summer will be evaluated for their effectiveness in preventing quiescent infections by fungi that subsequently cause decays in apple (NY-G, peach (NJ-B), and blueberry (NJ-C) during postharvest storage, and fruit receiving conventional fungicides will be compared. In addition, fruit samples from commercial organic farms will be similarly evaluated and compared with samples from conventional fruit farms. A novel method for inactivating defense mechanisms in apple skin will be employed to evaluate apple peel effects in limiting pathogen growth during storage. Hydrogen dioxide (OxiDate) will be evaluated for effectiveness in preventing postharvest decays of organic apples (NY-G). Pathogen populations on organic fruit receiving postharvest treatments with hydrogen dioxide will be compared with populations on non-treated fruit. 2c. Development of optimized application protocols for non-apple fruits: pears, tomatoes, peaches, melons, strawberries. Appropriate use of 1-MCP to enhance postharvest quality of pears, which tend to be more variable in their response to 1-MCP than apple and must fully soften before consumption, will be developed. Response to 1-MCP in pear appears to be even more dependent on fruit maturity at the time of application than that in apple, and at relatively high concentrations of 1-MCP, failure to ripen may result (Argenta et al., 2003; Gapper et al., 2006). Protocols will be developed using variations in 1-MCP concentrations and storage conditions to minimize unwanted effects on pear [CA, OR, USDA-WA]. Additional information will be collected on the benefits of 1-MCP for strawberries, blueberries, and raspberries [CA] and on peaches and melons [NC]. Variability among cultivars will be evaluated. Responses of tomato fruit to 1-MCP will be further studied [ON, NY-I, MI]. 2d. Establishment of optimal handling and storage conditions for problematic fruit. Treatment strategies to control scald by thermofogging to avoid disposal of unused liquid antioxidant will be developed for preventing storage scald in Anjou pears, and prediction techniques will be refined to better identify fruit that should be treated [WA-W]. Packing techniques will be determined to minimize the development of Lenticel Breakdown in risk prone apples [WA-W]. Objective 3: We will develop technologies and practices that optimize market returns and promote increased consumption of health-beneficial fruits through preservation or improvement of fruit quality attributes. Apples continue to be one of the fruits most purchased by consumers. We need to document the quality of this fruit to gauge effectiveness of current postharvest technologies and the relative appeal of fruit to consumers. In addition, although significant progress has been made on postharvest uses of 1-MCP, new studies of preharvest applications of 1-MCP to reduce preharvest drop, as well as continued studies of 1-MCP effects on postharvest quality, are needed. While apple research has traditionally been the primary focus of the group, we recognize the current need to expand our efforts to include other fruits. Health experts recommend inclusion of a variety of fruits in the diet to maximize benefits. As well, markets are expanding for traditional fruits such as melons, small acreage/high value fruits such as strawberry and blueberry, and some fruits new to U.S. markets, such as mango. All these fruits require tailored postharvest technologies to best maintain sensory attributes that appeal to consumers, and all contain antioxidants and other phytonutrients of interest to nutritionists, commodity groups, growers, and consumers. 3a. Apple cultivar responses to 1-MCP applied preharvest. Our focus will be on evaluating how cultivar and postharvest handling affect the continued commercial implementation of this product, with a primary emphasis on apples of importance to the Northeast. Many of these apples lose firmness quickly in storage and at retail, and could benefit greatly from the effective use of 1-MCP. The influence of different environmental and cultural conditions under which individual cultivars are grown will be evaluated by replicating efficacy trials across the U.S. and Canada [CA, BC, MA, MI, NY-I, NC, PA]. Changes in decay susceptibility of fruit receiving preharvest applications of 1-MCP will also be assessed to determine if preharvest applications of 1-MCP increases fruit susceptibility to postharvest decays caused by Penicillium expansum, Botrytis cinerea, Colletotrichum acutatum, Botryosphaeria obtusa, and Botryosphaeria dothidea [NY-G]. Potential adverse interactions between prehavest sprays of 1-MCP and captan residues commonly present on fruit during late summer will be investigated to determine if the oil that is used with the sprayable 1-MCP will enhance captan uptake into fruit or leaves where it will likely cause phytotoxicity [NY-I, NY-G]. 3b. Postharvest decay control in apples and blueberries. Preharvest sprays of Pristine fungicide (pyraclostrobin plus boscalid) will be assessed for effectiveness in controlling postharvest decays. Postharvest fungicides will be evaluated both for effectiveness in controlling decays on treated fruit and for effectiveness in eliminating Penicillium spores from harvest bins. Fludioxonil and pyrimethanil, used either alone or in combinations with captan, will be integrated into postharvest treatment strategies that will control decays, minimize selection for resistance to these new fungicides, and reduce numbers of spores that survive on bins that are process through the treatment drenches. [NY-G]. Specific fungicide mixtures, e.g., strobilurin and triazoles, will be tested in preharvest sprays to improve control of blueberry anthracnose and other latent infections [NJ-C]. 3c. Fruit appearance and eating quality. There are few published studies with quantitative data on the fate of fruit quality in U.S. markets following handling, storage, and transportation, although phone surveys of consumer preferences are common. Therefore, a project will be undertaken to determine how well apple quality holds up at the consumer level across the U.S. and Canada. Washington state apples will be purchased and evaluated by researchers for injury, disorders, and quality indices in 10 regions [WA, OK, CA, NS, ON, ME, MI, MN, NY]. Fruit will be sampled four times over a 12 month period and evaluated for firmness, SSC, appearance, and bruising. Fresh-cut fruits also hold great potential as a value-added product, with appeal and accessibility to time-constrained consumers. We will determine how cultivar, prestorage treatments, and storage regimes affect browning on fresh cut apple slices [ON], which is one of the biggest challenges limiting cut fruit appeal. In addition, fruit wounding through cutting operations can negatively impact respiration and carbohydrate metabolism. The response of apple cultivars to wounding will be explored [CA]. Pears continue to be elusive in giving a consistent response to storage regimes or treatments, showing variation with cultivar and production environment. Strategies to provide consistent, consumer-ready fruit of acceptable firmness and sweetness will be developed [CA]. Our intent is to conduct research complementary to that encompassed by S294, the multistate project on quality and microbial safety of all types of fresh-cut produce. 3d. Fruit phytonutrients/antioxidants and human health. The value of fruits as an integral part of a healthy diet is increasingly evident as results of long-term clinical and nutritional studies are published. Many of the most positive recent results on reduction of cardiovascular disease and cancer link the benefits to various phenylpropanoids (e.g., phenolic acids and flavonoids) and isopentenoids (e.g., carotenoids and phytosterols). U.S. commodity groups are interested in effects of cultivar, production systems, and storage regimes on antioxidant concentrations. For most researchers in our group, involvement of medical and nutritional interest in fruits depends on initial identification and quantification of antioxidants and other phytonutrients. Independent and collaborative studies will explore antioxidants and quality attributes of apple and non-apple fruits [WA, USDA-WA, NY-I]. Effects of mango extracts on oxidative stress in cultured cells will be explored and, in collaboration with a human nutritionist, active components of mango that improve glucose efficiency or prevent macrophage development will be determined [OK]. Blackberry selections of fall-fruiting (primocane-fruiting) types will be evaluated for quality and total phenolic and anthocyanin content [OK]. Collaborative studies with breeders and production horticulturists will determine changes in fruit quality and antioxidants with organic and extended season production systems [OK, AR]. Phenolic compounds with reported human health benefits in fruit flesh of wild and cultivated eggplant genotypes will be characterized and quantified [USDA-MD]. Cucumis melo reticulatus (cantaloupe) and C. melo inodorus (honeydew) fruits will be evaluated for variability in superoxide dismutase (a human antioxidant, anti-inflamtory supplement) [USDA-TX, NS]. Comprehensive metabolic profiling techniques will be employed to investigate water and oil-soluble antioxidant metabolism during apple storage [USDA-WA, USDA-MD]. Transgenic apple lines will be generated to increase the accumulation of the anti-inflammatory flavonoid quercetin in fruit tissues [NY-G]. The influence of quality attributes, including antioxidant properties, on consumer purchasing preferences will be evaluated [MN, NY-I].Measurement of Progress and Results
Outputs
- Document geographic distribution, seasonal, cultivar and storage protocol effects on apple quality, nutritional value and storage life.
- Identify antioxidant contents and anticarcinogenic properties of commercially important non-apple fruit crops of known genetic backgrounds
- Provide updated recommendations to the apple industry on strategies tailored for specific growing regions to avoid postharvest disorders and decays and maximize quality of Honeycrisp apples
- Document regional, varietal, and seasonal effects on the efficacy of 1-MCP as a preharvest application on fruit quality, nutritional value, and storage life.
- Integrated systems for controlling scald and postharvest decays will be developed and tested, then results will be provided to commercial packinghouse operators.
- Determine effective postharvest protocols for use on new genotypes and cultivars being used in non-traditional production systems (organic, season extension).
- Provide updated information to growers on the most suitable fruit cultivars for postharvest quality, in combination with sensory and nutrition information.
Outcomes or Projected Impacts
- Improved human health as a result of increased consumption of fruit.
- Consumers will have access to safer, more affordable, and better tasting fruit through improvements in fruit cultivars and improved handling practices.
- Fruit industry achieves considerable savings (potentially millions of dollars a year) from eliminating the use of unnecessary chemicals and reducing fruit loss in storage. The ultimate goal is to replace aqueous postharvest treatments of DPA and fungicides for apple fruit.
- Elimination of postharvest disorders, especially soft scald and bitter pit, and rots in Honeycrisp will allow the apple industry to realize maximum profits from this highly popular new apple cultivar.
- Knowledge about the susceptibility of apples to soft scald will be used in breeding programs for Honeycrisp progeny in order to develop resistant cultivars.
- Markers for apple crispness developed from gene expression data from different apple germplasm will provide a rapid screening method for apple breeder leading to apple cultivars with desirable eating quality.
- Orchard managers and producers will be able to determine cost effectiveness and benefits of using 1-MCP for pre or post-harvest applications.
- Use of 1-MCP on some fruit will enable producers to market a higher quality product to the consumer in an economically viable way, thereby narrowing the quality gap relative to fruit from off-shore production areas (especially in the off-season) and improving competitiveness.
- Packinghouse operators will adopt improved methods for controlling P. expansum while reducing exposure to harmful chemicals.
- Incidence of fruit with decay or disorders in retail store packages will decrease.
- Replacement methods for methyl bromide for postharvest insect control in fruits and nuts will be developed.
Milestones
(2009): <ul><li>Publish two or more studies on the effects of storage regimes on fruit and antioxidant composition. <li>Establish a website that summarizes all existing information about quality management of Honeycrisp apples. <li>Publish two or more studies of the effects of preharvest 1-MCP treatment on storability of apples.</ul>(2010): <ul><li>Complete studies that identify the active antioxidative components of fruit. <li>Identify postharvest handling methods that will reduce or eliminate browning disorders in 1-MCP treated apple fruit. <li>Publish two or more studies on the genetic and biochemical mechanisms of fruit ripening and quality. <li>Complete and publish evaluations of apple fruit quality before and after 1-MCP commercialization at the retail level. <li>Complete evaluations of small fruits in alternate production systems and storage system trials. <li>Initiate investigations into new apple cultivars and selections released from breeding programs.</ul>
(2011): <ul><li>Publish two or more studies on the effects of storage regimes on fruit and antioxidant composition. <li>Complete studies on the physiological mechanisms underlying bitter pit and postharvest pathogen contamination. <li>Publish two or more papers on underlying mechanisms involved in browning development of apple fruit. <li>Publish two or more studies on the genetic and biochemical mechanisms of fruit ripening and quality. <li>Complete investigations on strategies to avoid development of soft scald, bitter pit and fungal disorders of Honeycrisp apples. <li>Complete evaluations and publish a bulletin on small scale handling practices for NE growers. <li>Publish three or more studies in the effects of preharvest 1-MCP treatment on storability of apples and other fruit.</ul>
(2012): <ul><li>Complete and publish two or more studies on the biochemistry and genomics of superficial scald development. <li>Complete and publish Neural network analysis of Honeycrisp disorders. <li>Document changes in postharvest chemical use in the apple storage industry as a consequence of the integration of 1-MCP as a cultural tool. <li>Establish an internationally available website on storage disorders of apple fruit, with emphasis on new disorders associated with 1-MCP use.</ul>
(2013): <ul><li>Complete and publish two or more studies on the interactions between preharvest factors and antioxidant composition of fruit. <li>Publish a review on control of physiological disorders based on research of the NE1018 group. <li>Publish two or more studies on the genetic and biochemical mechanisms of fruit ripening and quality. <li>Provide information about fruit maturity and storage quality of new cultivars and selections in both scientific and popular articles.</ul>
Projected Participation
View Appendix E: ParticipationOutreach Plan
Results of this research will be made available through several means: Refereed publications, conference papers and proceedings, project reports, on-line sources (web), and industry reports. Several participants have partial extension appointments and therefore will develop outreach materials through fact sheets and other extension publications.
Organization/Governance
One person at each participating agency is designated, with approval of the agency director, as a voting member of the Technical Committee. Other persons at agencies are encouraged to participate as non-voting members. The Chair, Chair-Elect, Secretary, and Administrative Advisor will conduct the activities of the multistate project between annual meetings. Officers can be any member, including the official voting representatives. The officers are elected every second year by voting members and serve a two year term. A succession of officers from Secretary to Chair-Elect to Chair is normal, but may be adjusted depending on circumstances.
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