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 integrated ‘omics’ investigation from genetics, genomics, proteomic as well as metabolomics to identify development and control mechanisms of physiological disorders, especially ‘Honeycrisp’ disorders and superficial scald. A model for transcription factor control of pear ripening was suggested. Quantifications of secondary metabolites related to metabolism and nutrition quality will also provide a resource for nutritionists and marketers. Evidence of programmed cell death in degradative processes in banana fruit during ripening and over-ripening was provided as increases in several isoforms of protease and nuclease activities in peel during ripening and over-ripening.

Applied outcomes include the adoption of techniques for evaluation of harvest maturity and 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 harvest maturity and storage-ability of ‘Honeycrisp’ and ‘Ambrosia’ has been provided for adoption of that technology in North American apple industries. There is interest to evaluate also for ‘Gala’ apple which for which starch clearing has not been consistently useful in BC and work has been initiated at the industry

Information on the efficacy of dynamic controlled atmosphere storage (DCA) and delayed high CO₂ as non-chemical means of preventing storage disorders were generated and are being used to make recommendations useful to the North American apple industries.

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.

Information on several pre- and postharvest factors (such as ACU, canopy light penetration, excessive heat, 1-MCP, and CA conditions) that affect antioxidant systems affecting pear scald is being used to make storage decisions in the Oregon pear industry. New knowledge that becomes technique to reduce fruit scald susceptibility has been developed.

Fruit maturity studies on late-season apple cultivars were completed. ‘Cripps Pink’ (Pink Lady) has been shown to fully-mature in the mid-Atlantic Region.

Model temperature profiles are being generated on new sweet cherry cultivars to estimate potential shipping life based on expected accumulation of heat of respiration in palletized cherries. Meanwhile, pre-harvest calcium sprays with optimum application rate, timing, frequency, and calcium sources; PGR (e.g., GA₃, brassinosteroids) sprays at appropriate rate and timing; adding calcium in hydrocooling water at appropriate rates; and selecting MAP with right gas permeability which matches fruit respiration rate. The industry has been adopting these technologies quickly.

Applied postharvest treatments employing 5 or 10 mM oxalic acid applied on mango fruit has been reduced the postharvest incidence and severity of chilling injury symptoms. While, hot water immersion at 45^oC for 30 min followed by application of commercial carnauba-based coating was shown to have potential to maintain fruit appearance and consumer acceptance, and improve nutrient composition of orange fruit.

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 as well as OT, BC and NS Canada 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. NS Fruit Grower association annual 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.

Beth Mitcham, California, discussed the walnut storage and post-storage quality. Challenges with long-term storage due to 18:3 fatty acids (also decay and aflatoxin). Looked at relationships between water activity, RH, and rancidity and quality loss.

Rena Moran, Maine, reported the results from plum cultivar evaluation. Then she reported the results from Delta Absorbance (DA) meter on apple harvest maturity. Some relationship between starch index and DA reading (weak relationship) for both harvests were found. After storage - DA at harvest was highly correlated DA after storage. However, poor relationship between bitter pit and DA, modest relationship between diffuse flesh browning and low DA reading was found. No relationship for soggy breakdown was found.

Cindy Tong, reported the collaboration work on ‘Honeycrisp’ storage disorders with Maine and Ontario and determined the extent to which sugars and elemental content of fruit are altered in correlation with diffuse flesh browning, and studying the microstructure of peel of fruit with soft scald. Issues on DA meter failings as well as alternative (Felix F750 NIR meter), as an option for evaluating maturity was discussed.

Chris Walsh reported apple maturity and harvest date on scald on ‘Cripps Pink’ and ‘Granny Smith’ and research interest in finding a visible marker for superficial scald. Anthocyanin development seemed to be related with a loss in scald susceptibility for both cultivars. No obvious relationship between DA meter and susceptibility to scald.

Perkins-Veazie, North Carolina, reported on evaluation for postharvest quality attributes on strawberry selections. Pigments were evaluated and low amount of p-coumaryl hexose in one line may be related to anthracnose resistance.

Randy Beaudry, MSU reported the optimization of storage method for the controlled atmosphere storage of ‘Honeycrisp’ apple in Michigan and treatment with diphenylamine (DPA) just after harvest prevents CA injury.

Jun Song, Nova Scotia, reported employing an integrated ‘omics’ approach on storage disorders. From crossing of ‘Honeycrisp’ and ‘Ambrosia’ and other populations containing 340 offspring using linkage mapping, a potential marker region on Chrom2 and 3 were identified. While, soft scald development was not easily linked to the development of particular volatile profiles.

Forney reported his breeding project for strawberries. Correlations emerged between postharvest decay and firmness. Firmness was positively correlated with acidity, it seemed to be more susceptible to decay.

Chris Watkins, New York, reported the findings of new cultivars ‘Snapdragon’, a ‘Honeycrisp’ offspring) and New York 2 (‘Ruby Frost’, a 'Braeburn' offspring) that developed numerous postharvest issues including CO₂ injury and greasiness.

Chris also reported the ‘Honeycrisp’ storage related to bitter pit and soft scald. Correlations between various metabolites and disorders have been determined. Soft Scald late to develop, so a low temperature storage may be an option for a short duration. Ethanol and acetaldehyde concentrations were evaluated as a predictor of soft scald development.

Jennifer DeEll, Ontario, described the research optimization of storage regimes and 1-MCP application to reduce storage injuries such CO₂ injury and senescent browning. Further she reported that conditioning for one or two days at 10°C completely eliminated the chilling injury (in terms of mealiness).

Yan Wang, Oregon, evaluated regimens for improving ripening capacity of ‘D'Anjou’ pears. He reported that the accumulated chill units (ACU), which reduced chilling requirements markedly. Calcium spray affected chilling requirement too with higher Ca increased chilling requirement. It is also reported that the high levels of water soluble polyuronides associated with buttery juicy texture with low oxygen (0.8 to 1%) CA storage can preserve this texture after extended storage. Texture was also affected by Calcium - with high Ca associated with better buttery texture. Once fruit lost the ability to produce ethylene, they also became unable to make buttery texture.

Wang also conducted the study on control of superficial scald on pre- and postharvest factors. It seemed that the higher ACU and higher light seemed to be associated with improved resistance to scald. 1-MCP treatment of 100 ppb is becoming an industry standard, but it is as effective in commercial settings. However, 1-MCP is effective to reduce superficial scald when combined with low O₂. 1-MCP application at 150 and 300 ppb on Gem pear storage was effective to preserve crispy texture and completely prevented superficial.

Peter Toivonen (BC) reported his study on evaluation of 7 new advanced numbered apple cultivars (SPA628, SPA766, SPA1008, SPA1044, SPA1062, SPA1079 and SPA1080) for optimum harvest maturity recommendations has been completed. The I_AD index values were found to consistently correlate to postharvest performance (IEC, firmness and titratable acidity). He also generated a model temperature profiles to estimate potential shipping life based on expected accumulation of heat of respiration in palletized cherries.

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

Randy Beaudry, MSU discussed the importance of 1-MCP to apple industry and the challenges such as its negative impacts on aroma production and enhanced sensitivity to CO₂ injury. Use of 1-MCP has the potential to supplant the use of CA for this important apple variety.

Jun Song, Nova Scotia, reported a quantitative proteomic study on superficial scald disorder and effects of DPA and 1-MCP treatments. Eighteen significantly changed proteins were identified - 14 related to scald development and 4 that are decreased but increased by DPA and 1-MCP. Chlorogenic acid metabolism implicated, but 4CL (4-coumarate-CoA ligase) and a glutathione-S-transferase seem to be in scald development. Involvement of PPO in browning development of superficial scald is discussed and alternative browning pathways were suggested.

Chris Watkins, New York, described the application of ‘Harvista’ and DCA on storage of ‘Gala’ and reported that the DCA was very effective at reducing radial flesh browning. DCA was also able to eliminate core browning and delay appearance of stem end browning of ‘Gala’ and ‘Fuji’ from different orchards.

Jennifer DeEll, Ontario, reported the effect of the application of ‘Harvista’ and DCA on storage of ‘Gala’ and reported that slowing the cooling had an impact on reducing browning. ‘Harvista’ treatment reduced flesh browning and found to be better at reducing stem cracking compared to ReTain. ‘Harvista’ was also better at slowing maturation.

Multiple applications of SmartFresh were beneficial on firmness at 6 months.

Yan Wang, Oregon, evaluated 1-MCP as an alternative to Ethoxyquin for controlling superficial scald in D'Anjou pear. A concentration of 100 ppb of 1-MCP reduced black spot and scald. Effect of 1-MCP responses were a little unpredictable and seemed to depend on fruit maturity. Less mature fruit were more beneficially affected by 1-MCP.

Peter Toivonen, BC, reported the effects of 1-MCP for ‘Ambrosia’ apple quality and disorder development in CA and DCA-RQ storage systems. He also found that background colour of ‘Ambrosia’ apples is the most reliable indicator of maturity under BC growing conditions.

Objective 3. Investigate the metabolic and physiological processes that underlie the responses of fruit to postharvest technologies.

Beth Mitcham, California, reported the changes in gene expression for European pear (‘Bartlett’) and determined the influence to chilling, maturity and the relationship to softening. Fruit became responsive to exogenous ethylene at the transition between stages 2 and 3. After stage 3, exogenous ethylene was no longer required. Several important genes were found to be linked to the transitions between maturity stages. Low temperature treatments on ‘Bartlett’ can accelerate ripening. A number of genes and transcription factors shifted in response to the treatments. Most ethylene-related genes increase during ripening and those associated with jasmonic acid metabolism decline. A model for transcription factor control of ripening was suggested. ACO seemed to be the most promising gene to predict the rate of softening.

Jeff Brecht, Steve Sargent and Donald Huber, Florida, evaluated the programmed cell death on banana during ripening and over-ripening. Signs of DNA degradation (DNA laddering) were found once brown spots were found on the skin. The internal discoloration ('Corte negro' or 'Cutting black') of mango was determined to be a chilling injury symptom. The effect of nitrogen rate and application method was evaluated for peach and it found that the highest N rate (240 lb/acre) was not problematic. Fruit were firmer at the time of harvest and after 3 days ripening. Little effect on nutritional components other than carotenoids, which were low in the lowest N treatment.

The use of hot water immersion and coating material was evaluated for orange fruit. An optimal time and temperature were determined for orange fruit and several coatings were evaluated. With carnauba, a 5% O₂ and 5% CO₂ atmosphere could be maintained. The impact of pre-storage application of oxalic acid to reduce chilling injury in mango was determined and suggested that the oxalic acid improves the metabolic activity of antioxidant systems.

Randy Beaudry, MSU, continued research on in apple and other fruit for elucidation of potential pathways for the synthesis of esters and other important aroma compounds are still being elucidated. Identified the findings on citramalate and ester formation and sequence the promoter regions of the citramalate synthase and isopropylmalate synthase genes form apples.

Penny Perkins-Veazie, North Carolina, evaluated the pigment stability in Muscadine wine grapes lines with an interest in identifying with better stability.

Jun Song, Nova Scotia, conducted a targeted proteomic investigations employing MRM to look at different metabolic pathways including those associated with ethylene, aroma, pigments and antioxidants. In strawberry, antioxidant metabolism was implicated in ripening.

In another quantitative proteomic study on banana fruit in response to high temperature and ethylene treatment revealed 91 significantly changed proteins that were found to quantitatively change. Cluster analysis on these 91 proteins identified 7 groups of changed proteins. Ethylene treatment and storage at 20°C induced 40 proteins that are correlated with pathogen resistance, cell wall metabolism, ethylene biosynthesis, allergens and ribosomal proteins, and it repressed 36 proteins that are associated with fatty acid and lipid metabolism, redox-oxidative responses, and protein biosynthesis and modification. Ethylene treatment and storage at 30°C induced 32 proteins, which were mainly similar to those in group 1 but also included 8 proteins in group 3 (identified as chitinase, cinnamyl alcohol dehydrogenase 1, cysteine synthase, villin-2, leucine-tRNA ligase, CP47 protein and calmodulin) and repressed 43 proteins in 4 groups (groups 4-7), of which 6 were associated with photosynthesis II oxygen-evolving protein, the photosynthesis I reaction center, sugar metabolism, the redox-oxidative system and fatty acid metabolism. Differences in the response to ethylene and holding temperature at 30°C were also revealed and have been discussed.

In order to gain better understanding on physiological disorder and effect of delayed cooling, quantitative proteomic changes in 'Ambrosia' were found in response to chilling and delayed cooling. Approximately 80 proteins were found to be linked to preconditioning and provided physiological evidence of delayed cooling at proteomic level.

Song and Forney also reported that three groups of volatiles were implicated - an acetate ester, butyl acetate, hexyl butanoate and hexyl hexanoate may be related to disorder development.

Chris Watkins, New York, reported the study on the pattern of starch clearing in apple and found that the onset of the degradation at the top was primarily a function of the total accumulation - with more starch content being related to later clearing. Clearing took place soonest at the stem end of the fruit. The attempt is being made to connect ripening related genes with this pattern of starch clearing.

The relationship between plant growth regulators (PGRs) and IAD values (DA meter) in apple was determined. Harvista and ReTain disassociate ripening and softening behavior from the IAD reading. So IAD readings are of little value for fruit in which ethylene biology is being influenced.

Research working on apple cuticles employing metabolomic, proteomic and molecular characterizations is being conducted by Jocelyn Rose and is interacting with S. Brown on germplasm available in New York plantings.

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 QTL analysis of soft scald in Apple (Malus x domestica Borkh.).
• Published one study on proteomic changes of superficial scald development and DPA and treatments.
• Published two studies using targeted proteomic technique on flavor and flavonoids biosynthesis in strawberry fruit.
• Published multi studies on control of superficial scald in pears under the storage and postharvest treatments.
• 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;
• 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;
• Having laid an experimental foundation, the next milestone will be to associate these phenotypes and chemotypes with resistance or susceptibility to postharvest disorders and loss of quality during such treatments, and then to apply the gene expression profiling technologies to gain insights into the underlying molecular pathways. This in turn will be correlated with gene expression networks in the fruit epidermis.