Brief Summary of Minutes of Annual Meeting

SHORT-TERM OUTCOMES

Short-term outcomes for postharvest research are both fundamental and applied. Fundamental outcomes include the sharing of scientific findings and the development of collaborative projects. Applied outcomes typically involve adoption of technologies or practices by industries involved in perishables storage.

Fundamental outcomes include an assessment of mass spectrometry as a tool to identify the proteins and metabolites produced by perishables to describe their responses to storage environments or to describe the impact due to germplasm for a number of commodities. Quantifications of secondary metabolites related to nutrition quality will also provide a resource for nutritionists and marketers.

Applied outcomes include the adoption of techniques for minimizing injury due to low temperatures and stressful storage atmospheres on pome and stone fruit. Of particular note, the North American apple storage industry has adopted recommendations by members of the NE1336 to use delay of cooling (prestorage conditioning) to prevent low temperature injury of Honeycrisp apples. In addition, delay of cooling and DPA use has also been adopted for prevention of injury from low O₂ and elevated CO₂ atmospheres.

Information on the efficacy and applicability of the DA meter for estimating fruit chlorophyll has been used in the cautious adoption of that technology in North American apple industries.

Information on factors associated with the development of internal browning of Gala and other apple varieties susceptible to internal browning disorders has been shared with North American apple industries, and storage operators are modifying their storage regimens where feasible.

Information on the efficacy of dynamic controlled atmosphere storage (DCA) as a non-chemical means of preventing storage scald was generated and is being used to make recommendations useful to the North American apple industries.

Metabolite levels of harvested apples are being tracked and information given to storage operators in Washington orchards to support their storage decisions.

Information on environmental factors affecting pear scald is being used to make storage decisions in the Oregon pear industry.

Recommendations on the use of 1-methylcyclopropene (1-MCP), and ethylene action inhibitor have been used to make use recommendations for the US and Canadian apple industries and the California pear industry. Similar information is being developed for the Florida avocado and mango industries.

Oxalic acid applied to mango fruit postharvest was discovered to reduce incidence and severity of chilling injury symptoms, which was associated with enhancement of membrane integrity and the fruit antioxidant system and energy cycle.

1-MCP was found to interact negatively with quarantine hot water treatment (QHWT) for mango, while ripening was delayed in fruit treated with 1-MCP without QHWT without injury. Thus, 1-MCP may be more useful for mango markets that do not require mandatory QHWT.

OUTPUTS

Tangible outputs in the form of peer-reviewed publications are listed under 'Publications'. Each of the participants in the NE1336 routinely generate presentations, factsheets, and reports to their respective industries. Extension publications include the Maine Apple Pest Report, NY Fruit Quarterly. In addition, states such as CA, ME, MI, NY and WA have extensive formal industry venues for presentation of results to growers. These include Storage workshops in MI and NY, the New England Vegetable and Fruit Growers Conference and Trade Show, The NY Fruit and Vegetable Expo, Carolinas Fruit and Vegetable Expos, the NC Winter vegetable meeting, the SE Fruit and Vegetable Expo, Annual Hood River Winter Horticultural Meeting, Pear Packers Pre-harvest meeting, Minnesota Apple Growers Association, and Great Lakes Horticulture meeting. UC Davis runs a number of specific outreach courses, e.g. Fruit Ripening and Retail Handling Workshop, each year.

ACTIVITIES

Objective 1. Optimize storage regimes for existing apple, pear, plum, cherry and berry cultivars, with emphasis on new cultivars arising from breeding programs in NY, BC, ON, MI, MN and WA.

Peter Toivonen (BC) opened this discussion with results from his studies of apple maturity in new apple cultivars and numbered selections. Maturity in the new cultivars such as Ambrosia and breeding selections has been difficult to monitor as starch patterns have not been consistent from year to year, due to erratic weather. Ground color using the DA meter appeared more stable than starch but is just one tool available. To get a better understanding of maturity, they use three major maturity criteria in their analyses at Summerland. Internal ethylene is not always closely linked to the other maturity indices in some of these new selections.   Lower-ethylene apples with non-traditional maturation patterns appear to have been selected recently by fruit breeders. As considerable interest in Ambrosia and selections from the SPA program, there was much discussion of the maturity studies in BC.

Toivonen also reported on his studies with the Delta A (DA) meter, showing that measurements differed depending on the light environment in the tree. A reading on the back (unexposed) side of the fruit was the most reliable in his studies. Temperatures also affected the DA readings; this was particularly affected by warm night temperatures.

The consensus was that the DA meter measures the chronological age of the peel, but variation in chlorophyll can also occur in the peel. Watkins (NY) said it was helpful but not absolute for each fruit. When the meter reads zero, that certainly measured a senescent fruit. On the other hand, it has not been so easy to demonstrate the Nova Scotia maturity window using the meter. Peter Toivonen, (BC) agreed with the group in that it puts an additional maturity tool in the postharvest toolbox.

Chris Watkins (NY) discussed similar issues encountered when judging harvest maturity of NY 2 apples. He found a three to four week period where little changes in maturity indices are seen although major changes in storage life occur in this time period.

Sweet cherry work on new cultivars in BC was also reported.   A marked difference between 3 C and 0.5 C pre-cooling on respiration rate and likely storage life was shown, which were based on fruit respiration. In the resulting discussion, it was mentioned that a flavor note in sweet cherries is malic acid, not benzaldehyde which is a note in tart cherry.

Chris Walsh (MD) reported briefly on internal breakdown in Olympic Asian pear which is widely recommended due to its fire blight tolerance. Internal breakdown has been particularly troublesome for the past two seasons in the mid-Atlantic region, possibly caused by hot, dry summer weather.   Peter Toivonen (BC) mentioned that the symptoms in Olympic pear resembled those he had seen in Braeburn apples with internal breakdown.

Randy Beaudry (MI) discussed studies on HoneyCrisp apples, where he used a temperature-time matrix to study carbon dioxide injury. The only preventative measure appeared to be the use of diphenylamine (DPA), which protected fruits at 1000 ppm. Fermentation volatiles were also measured in this study, and the greater the fruit damage, the greater the level of these volatiles measured. Beaudry concluded that fermentation products were a byproduct of the damage, rather than an inducer of the damage. Discussion following this, centered on DPA usage and the potential problems in its long term release from bins in the packinghouse.  

Chris Watkins (NY) continued discussion on DPA. He believes it is likely to lose its EPA registration soon. Delayed controlled atmosphere (CA) storage appeared to be increasingly valuable and needs further investigation, along with the application of 1-MCP to prevent scald. While peel greasiness was increased by delayed storage, delayed CA appears to have positive effects and appears to be a valuable antidote to CO2 injury. If growers cannot use DPA, delayed storage appears to be their second-best strategy.   When conducting New York trials, senescent breakdown and bitter pit, were not affected by delayed CA treatment. Susan Brown (NY) noted that similar postharvest problems have also been found in fruit from Honeycrisp seedling trees.

Stem end browning in Gala was also mentioned. While some areas have not reported it, Chris Watkins (NY) mentioned that it has been seen in apples grown in New York, Ontario and Brazil. One hypotheses is that while ethylene synthesis and action may be affecting some aspects of maturation, but other non-ethylene related changes continue to occur. Regal Gala (Fulton) is more mature and cracks easier than other selections. As such it appears to also be more susceptible to internal browning.

Gala problems were also discussed by David Rudell (WA) who mentioned issues with fruit packers in Washington State. Serious disorders were discussed, including Gala stem-end browning, diffuse flesh breakdown, and a ‘baked apple effect,’ likely caused by box liners. Dave Rudell also mentioned that Jim Mattheis (WA) has a HortScience paper in press which will discuss these postharvest problems in detail.

Jennifer D’Ell (ONT) reported on her recent studies of mealiness in peach and nectarine fruit flesh. To deal with this, she studied a half-dozen cultivars to learn about cultivar differences but was surprised to find that mealiness came on within a week of storage from fruits in Ontario. Beth Mitcham (CA) and Toivonen (BC) recommended future trials with 1-MCP and then possibly holding them at room temperature.

The Nova Scotia report was given by Cheryl Hampson and Charles Forney who are working with genetics, genomics and proteomics tools to study soft scald in Honeycrisp. Gene sequencing technique is being used to look at the markers. There is also a second population of Cheryl Hampson’s (Ambrosia x HoneyCrisp) under study. The breeding populations showed a variation in disorder incidence. At this point QTL regions on chromosomes 2 and 3 appear to be correlated with soft scald development. Beaudry (MI) suggested that the group needed to develop a project to find a genetic solution to the Honeycrisp disorder susceptibility.

Charles Forney (NS) then discussed studies screening strawberry genotypes for phenolics and chemical profiling, and raspberry genotypes for their storageability. Raspberry storage treatments combined 12.5% carbon dioxisde and 7.5% oxygen. Physiological decay was reduced by high CO2, but there was also a loss of firmness. Ethanol production was evident in raspberries stored at 2 % oxygen.

Yan Wang (OR) reported on a series of projects studying pear scald. Fruit at the lower elevations with accumulated cold units was more susceptible to scald.   Fruit with lower calcium content was also more susceptible to scald.

Superficial scald and antioxidant capacity appear to be negatively correlated in this work.   Treatment with 1-MCP and long CA conditions reduced scald and low-oxygen injury. Treating with 100 ppb MCP in the laboratory worked perfectly, but in packing houses, fruits with the same treatment showed scald. Randy Beaudry (MI) mentioned the competition that occurs in a storage room between wood, cardboard and the fruit.   He suggested increasing the commercial level 1-MCP and that they should also quantify the actual level in the room. The suggestion was to use the highest treatment level possible that still allows pears to ripen. Gem pear was also studied in Oregon where harvest at ten to twelve pounds is used for commercial maturity. At that range of maturity, Gem fruit still retain a five-month storage life. Wang (OR) also reported that Gem fruit did have a problem with delicate skin.  

Calcium uptake in cherry was studied using calcium hydroxide in Oregon. Randy Beaudry (MI) mentioned that the deliquescence point and humidity were determinants of calcium uptake. When the calcium deliquesces, it will be more likely to penetrate the fruit.   Higher concentration of calcium were correlated with less pitting after shipping.

Modified atmosphere (MA) liners worked well to preserve cherry stem quality, but did not prevent pitting of the fruit.   Shippers in the Pacific Northwest are seeking four weeks to six weeks storage life, with five weeks required for shipping sweet cherries to Asian markets.  

Ozone in packing houses and storability was also discussed in the Oregon report where Bosc pears are having decay problems in storage. Ozone monitors are used to keep the level at 800 parts per billion (ppb). Since ozone is surface active, it cannot control latent infections. Secondary effects of ozone were also discussed along with its suitability for other crops and in the postharvest handling of organic produce.

Objective 2. Investigate the effects of 1-MCP technology on fruit quality and storage disorders, and its interaction with cold storage and CA technology.

Jennifer D’Ell (ONT) reported on a joint projects in Canada to control soft scald using many of the same treatments used for Honeycrisp on Ambrosia. They were using a short delayed cooling period and found that 1-MCP could have different effects on fruit from different orchards. MCP did affect firmness, but seemed to have far less impact on Ambrosia than Honeycrisp. The heat stresses faced of 2015 may have affected Ambrosia, which is planted in the hotter regions of the Okanogan Valley.

Studies in California to optimize the effectiveness of 1-MCP on Bartlett pears were covered in depth. Beth Mitcham (CA) reported that the California pear industry wants the benefits of MCP but needs fruit to be able to ripen in seven days. She summarized data from a large study conducted by Andrew McNish, testing the effectiveness of this compound on sensory quality. Fruit were harvested during the picking season and then ripened. Sensory evaluations were conducted on fruit of the same firmness by 12 trained panelists.   Fruit treated with 1-MCP was viewed as far better by the panelists as the fruit appeared to have a more stable taste profile. Differences in sugar and acids were also measured between treatments. In addition, Beth summarized the work being conducted on methods of 1-MCP application and new commercial products that are being tested for the California pear industry.

Jeff Brecht (FL) summarized work conducted in Steve Sargent’s lab on Florida avocados. Fruit can have a senescent peel blemish, and 1-MCP treatment reduces that peel damage. While this reduces the blemishing, it accentuates asynchronous softening, which in turn can be eliminated by a four-day ethylene treatment.

Mango studies are also being conducted in Florida with 1-MCP and hot-water quarantine treatment. Surface blemishes were seen on 1-MCP treated fruit receiving the hot-water dip. This treatment does not appear to have a potential for hot-water treated mango. 

Jackie Nock (NY) described Cornell studies testing dynamic chlorophyll fluorescence measurements in small CA chambers. By measuring fluorescence hourly it is possible to minimize oxygen levels until stress is seen, and then increase oxygen levels in the CA room slightly. She was able to take McIntosh to 1.1 % oxygen and Delicious to 0.6 % oxygen.   Two fruit per orchard, representative of the fruit held the storage room were monitored in the chlorophyll fluorescence measurements. Fruit stored in Dynamic CA (DCA) generally did better than CA-stored fruit held in a standard room. DCA stored fruit firmness was good when the storage was opened, but then decreased rapidly after seven days. Consequently, 1-MCP would also be required. Without 1-MCP the treatment would lead to attractive, but soft fruit. Dynamic CA appears to reduce a host of disorders, but vascular browning and flesh browning were not affected by this technology. 

DCA also appeared to provide a non-chemical method for scald control. During the past year Hudson Valley apple fruit had visible peel disorders, while fruit from Western New York had internal problems. Cortland didn’t appear to respond to DCA. While this was not the purpose of the study, they noted striking differences among ethylene levels and maturity in commercial orchards. Watkins felt that DCA was less effective than the standard treatment of 1-MCP.   Flesh browning in Empire is frequently a problem and warmer storage temperatures, and 1-MCP appears to exacerbate this problem.   Late-harvested, over-mature fruit appears to be related to internal browning. Earlier harvest by Ontario growers appears to reduce the problem for them. Empire is particularly difficult to handle as one week’s delay in harvest date can make a major effect on internal browning in storage (Watkins, NY).

Jennifer D’Ell (NS) reported on a series of trials with Harvista, including the use of surfactants, treatment dates and cultivar effects in the field. She also reported on the use of multiple applications of SmartFresh after harvest. It is sometimes necessary to treat more than once due to slow filling of storage rooms. A second 1-MCP treatment improved firmness retention in late-harvested Empire. Varying effects were seen on other disorders, but this did not affect internal browning. Studies are already underway to test whether carbon dioxide buildup during room loading may contribute to the problem. Not flushing the room, and not adding lime may allow injurious levels of carbon dioxide to accumulate.  

Yun Wang (OR) reported that the standard material, ethoxyquin for scald control in pears is no longer an option, and 1-MCP was tested as a replacement. It has to be applied within three weeks of harvest to control scald. The goal is to extend pear storage life and reduce the percentage of fruit going to the cannery. Many growers are applying aminoethoxyvinylglycine (AVG) prior to harvest. Applying AVG one day prior to harvest showed the greatest effect in these trials, but the pre-harvest interval is currently seven days. Applications closer to harvest could reduce the rate of product required, reducing pesticide usage while simultaneously saving money for the growers.

Objective 3. Develop technologies and practices that optimize returns and promote increased consumption of health-beneficial fruits through preservation or improvement of fruit quality attributes.

The discussion began with a presentation by Beth Mitcham (CA) reporting on calcium deficiency disorders of tomatoes and modifications of PME. This work has characterized PME binding sites for Ca in cell wall and reduced calcium levels in the apoplast. This binding begins in the columella and is correlated with blossom end rot. 

Beth also reported on the stages of pear maturity, differentially expressed genes, responsiveness to ethylene, and their ability to ripen without additional ethylene.   This work noted changes in both auxin-related genes and ethylene-related genes.   They also reported on low temperature conditioning and gene expression as well as the effect of 1-MCP on transcription factors and cold-expressed genes. They found that firmness appeared to be well correlated with ACO and are now studying the role of non-ethylene responses, searching for a marker that would better predict responses to 1-MCP.

Jeff Brecht (FL) presented work from Florida on a variety of studies carried out on a number of fruit and vegetable crops. He began by briefly summarizing the role of ethylene and programed cell death, which is an active process. 

Brecht also discussed the current status of Florida’s low-chilling peach industry with a goal of producing tree ripe fruit. Additional attention to this 1,500 acre industry is likely as citrus producers turn to alternate crops. The market window for Florida peaches will be late-April to early-June, with the goal of marketing tree-ripe fruit. Jeff Brecht is working with Harry Klee and other plant breeders and molecular biologists with the goal of producing specialty crops such as peach, tomato, strawberry and basil that have excellent consumer acceptance. This led to a discussion of chilling injury and treatments used to reduce its effects. Hot water treatments can reduce chilling sensitivity, with the highest temperatures and shortest dwell time having the greatest effects. This is thought to lead to the up-regulation of carotenoids, phenolics and reactive oxygen species. Stimulation of the antioxidant system can be protective, even to chilling stress.   Treatments of 52C for five minutes, or 54C for 2.5 minutes have been effective on tomato, one day past green-mature.

Tianbo Yang (MD-2) presented an overview of Wayne Jurick’s research studies of postharvest fungicide resistance and has found multiple resistance genes in Botrytis.

In addition, Jurick has analysed the genome of Pennicilium expansum for potential mycotoxins production, finding a series of secondary metabolism clusters related to mycotoxin formation.  

They also reported calmodulin gene expression in tomato, which is involved in fruit enlargement to ripening. The signal is up-regulated at the breaker stage. The relationship between calcium and ethylene is being studied, while searching for the up-regulated ripening related genes. Additional studies are comparing the relationship between the calmodulin gene and Botrytis infection.

Penny Perkins-Veazie (NC) reported on chemical studies of secondary compounds in muscadine grapes. She reported on a series of studies of pigments in the peel and the need for heat-stability to improve the quality of muscadine grapes for fresh-market sales and quality wine production. Penny also reported on testing products for postharvest use by organic producer, focusing on essential oils as a replacement for producers who do not wish to use chlorine in the product wash water. They have been testing eugenol and iso-eugenol but have questions of cost effectiveness. In addition, these cannot be used on all crops as they hve been detrimental to lettuce. Thyme oil turns lettuce brown and unsaleable.

Nova Scotia reported the results of their LCMS work studying peptide sequences. Jun Song (NS) described the current broad work which would will eventually target metabolic pathways.   He reported the identification and analyses of 1600 proteins and 80,000 peptide sequences. They are focusing on strawberry, searching for protein clusters involved with the synthesis of aroma volatiles. An eventual goal is to have the ability to make comparisons between anthocyanin regulation in climacteric and non-climacteric fruits.

Jennifer D’Ell also reported on seasonal weather conditions and their effect on various fruit qualities. Growers in Quebec report that fruit appear to be getting softer at harvest. Computer modeling has been used to study the effect of seasonal variations in temperature and rainfall on soft scald and soggy breakdown development.  

Metabolite level attributable to soft scald risk was conducted using metabolic profiling of 17 orchards in Washington State (Rudell, WA). Assessing metabolites at harvest proved to be difficult, but did work better in stored apple fruit. Rudell likened this to the greater value of a heart stress test done on a treadmill. A number of genes are upregulated early in cold storage. Upregulation of genes involved in disorders occurs first, then the metabolic changes are discernable a few weeks later.

PAL and LOX were upregulated in fruit that eventually showed soft scald symptoms. Orchards that weren’t at risk appeared to have fewer genes associated with isoprenoid biosynthesis.   Measuring farnesyl esters in the fruit also appeared to be related to a lower risk of soft scald. Rudell reported on temperature conditioning and partial metabolic analyses, measuring ethanol, ethyl acetate and soft scald tissue damage. They found that elevated carbon dioxide always led to high succinate concentrations, but not always tissue damage. This contradicts the succinic acid story published previously in Nature by Hulme.

MILESTONES

• Delivered protocols to small-scale producers in the NE for harvest and storage of novel plum and apple cultivars;
• Published recommendations for minimizing chilling and CA injury of Honeycrisp and other sensitive apple cultivars;
• Published a paper on preharvest factors that affect Honeycrisp apple storage;
• Published one study on harvest and storage of new plum cultivars;
• Presented findings to stakeholders and published at least two papers on the links between metabolic processes with different apple and peach postharvest disorders;
• Provided the pear and blueberry industries with the optimum MAP conditions, high CO₂/O₂ injury thresholds as influenced by temperature fluctuations, and identify films with the right gas permeability for long-term cold storage and long-distance sea shipment;
• Published studies on pear MAP;
• Characterized lipoxygenase enzymes in apple and determine changes in their expression with shifts in fatty acid substrates. Evaluate the potential for the involvement of the 2-carbon fatty acid synthetic pathway in the formation of short-chain precursors to esters;
• Published one study on the involvement of lipoxygenase in aroma development in apple;