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NE103: Postharvest Physiology of Fruits

Annual/Termination Reports (SAES-422): [04/08/2003] [06/24/2003]

Date of Annual Report: 04/08/2003

Report Information:
  • Annual Meeting Dates: 08/09/02 to 08/11/02
  • Period the Report Covers: 10/2001 to 09/2002

    • Participants:
    Brief Summary of Minutes of Annual Meeting:


    URL: Copy of minutes

    Accomplishments:
    Six new apples varieties grown in MA, PA and NC were stored for up to 6 months in either air or CA conditions at Penn State and evaluated for internal ethylene, firmness and acidity after storage. A limited number of samples were treated with 1-methyl cyclopropene (1-MCP) (PA). Honeycrisp storage characteristics varied greatly. Arlet developed greasiness in storage. Shizuka continues to perform less well than Mutsu. Cameos flavor is that of a much improved Delicious and stores better, but it is not as attractive. Florina, a scab resistant cultivar, does not maintain its flavor well during storage (MA). Incidence of soft scald and soggy breakdown in Honeycrisp apples was enhanced by late harvest and low storage temperatures, and associated with accumulations of acetaldehyde, ethanol and ethyl acetate in the flesh. (NY, Ithaca). Collaborations with the NC-140 rootstock study showed that rootstock appears to influence the maturation rate of Gala apples. (NC)

    Stratagies to define and optimize the quality of Washington apples, determine the potential deterioration of apples during transport and distribution, and evaluate the quality of Washington apples in retail stores in the USA are being developed (WA). The later is a cooperative study with CA, PA., NY, NC, MI, and SC. Additional studies will utilize nondestructive methods to evaluate edible quality (WA). We are also determining the relationship of firmness and soluble solids to the acceptability of Gala and Red Delicious apples to consumers (WA, OR, NZ)

    A 30% CO2 atmosphere appears optimal for storage of cranberry (NY, Ithaca). Large genotypic variations in antioxidant activities of nectarines, peaches, and plums are closely related to their total phenolics content. (CA). The magnitude of difference between postharvest-life based on flavor and that based on appearance of strawberries varies among cultivars and storage atmospheres. (CA). The minimum safe temperature for plantains is 10˚C (as compared to 14˚C for bananas) (CA). The optimal atmosphere for storage of pomegranates is 5 kPa O2 + 15 kPa CO2 at 7.5˚C and 90-95% RH (CA). Anjou pears stored for up to 2 months at 30F could be pre-conditioned with 100 ppm ethylene in-transit for 7 days at 45F or 3 days at 60F. Pre-conditioned fruit arrived in the retail markets with proper ripeness and good dessert quality (OR). Consumer acceptance of peaches is highly related to SSC:TA rather than SSC or TA alone (CA).

    1-MCP studies have focused on the effect of storage temperatures, with the aim of minimizing the risk of chilling injury, and on developing maturity recommendations that will result in maximum benefit of the compound. 1-MCP does not appear to allow higher storage temperatures to be employed (NY, Ithaca), although it did protect fruit from a temporary malfunction of refrigeration equipment (CA). 1-MCP delayed apple aroma formation relative to untreated fruit after storage. The delay was initially 30 days at room temperature and decreased to approximately 5 days after 5 months RA. Controlled atmosphere storage delayed aroma recovery even more severely. ReTain treatment prior to harvest did not alter the response of apple fruit to 1-MCP as long as ReTain-treated fruit and nontreated fruit were harvested at the same maturity (MI).

    Treatment of Golden Delicious apples with 1-MCP concurrently with ethylene at 65-190 ppm effectively delayed but did not prevent fruit ripening and controlled decay (MD-USDA). MCP was very effective in inhibiting scald development in Granny Smith apples kept at 1oC for 190 d. In addition, it greatly decreased the rate of fruit softening. Similar results concerning fruit texture were observed with "Gala" apples. In both fruits, 1-MCP suppressed the rise in -farnesene and conjugated trienol content (MD).

    The group also explored the benefits of 1-MCP treatment for fruit other than apples.
    Pre-storage treatment of 100 ppb 1- MCP inhibited the normal ripening process and the development of superficial scald disorder of dAnjou pears after storage in air at 30F for 5 months (OR). Multiple applications of 1-MCP during pear storage can extend the effects on fruit ripening if repeat applications are put on before the 1-MCP effects are completely lost (CA). The efficacy of 1-MCP in delaying ripening of partially-ripe bananas was too inconsistent for commercial application (CA).

    Use of 1-MCP on harvested fruit to inhibit maturation can predispose fruit to decay, but heat treatment or application of a biological antagonist are capable of preventing this increase in decay. The antagonist was most effective in controlling bitter rot, whereas heat treatment was better for control of blue mold (MD-USDA).

    Modified atmosphere packaging and a mixture of biocontrol organisms maintained postharvest life of red raspberries. Aroma retention was particularly sensitive to MA (WA, Pullman). Treatment of blueberries with UV-C light does not decrease decay (OK). Apricots and plums stored at 00C do not benefit from pre-storage fumigation of thymol vapor (ONT). Neither incidence nor severity of brown rot was affected by constant ethylene exposure on stone fruits wound inoculated with Monilinia fructicola. Similarly, ethylene did not affect gray mold nesting ability on table grapes artificially inoculated with Botrytis cinerea (CAEthyoxyquin and diphenylamine were most effective among a group of antioxidants and fruit coatings at reducing Bartlett pear fruit susceptibility to skin browning from vibration damage.

    A series of treatments are under exploration for control of insect pests that interfere with trade of fresh fruit. Treatment of table grapes with Silwet L-77 can provide effective control of numerous surface pests without harm to grape quality. Treatment of Bing sweet cherries with hot water to control codling moth larvae was fairly well tolerated, but stem quality problems will likely limit the use of this treatment method. Radio frequency treatments show more promise.

    Antisense ACS ‘Royal Gala‘ fruits had reduced ethylene production and softening indicating improved storability (NY, Geneva). When 1-MCP was used to inhibit the onset of the climacteric, the accumulation of ACS transcripts was completely inhibited while there was no effect on expression of the ACO gene. Expression of the ers1 ethylene receptor was also inhibited (MD). Bicarbonate and ascorbic acid activation of 1-aminocyclopropane-1-carboxylate (ACC) oxidase has been characterized (MI).

    Several studies are addressing the development of aroma in apples. ‘Redchief Delicious‘ apple fruit tissue was analyzed for the ability to metabolize 1-pentanol and synthesize constitutive esters and alcohols under anoxic and aerobic conditions. The biosynthetic rates of all esters increased as a result of air exposure (WA, Pullman). ADH is up-regulated in stressed tissue and particularly under anaerobic or low O2 levels. ADH has broad substrate specificity for alcohols and aldehydes and may serve to detoxify noxious metabolites in concert with the activity of alcohol acetyl transferase (MI). Banana fruit produced esters well after the biosynthetic capacity developed. It appears that alcohol supply initially limits ester production. Late in ripening, unsaturated esters increase, suggesting membrane breakdown helps supply precursors during senescence (MI).

    Apples receiving the most postharvest light produced the most anthocyanins. Optimal color development after harvest was achieved at 20-25 C, while at lower temperatures, color development was slowed. Reversibility of lychee pericarp red color in relation to pericarp pH, activity of polyphenol oxidase, and particle size of brown pigment is under study (ONT).

    Following CA storage analytical and sensory trials were conducted on fruit that were exposed to naturally occurring volatile components. Sensory panels were able to detect a significant difference between treated and control fruit but had no preference (PA). A consumer sensory evaluation of 1-MCP treated Red Delicious resulted in no significant flavor differences between treatments but a significantly higher texture associated with 1-MCP treatment was found (PA).

    Our studies suggest that insects damage plant organs using cell wall-degrading enzymes, much like pathogens do and that plant defenses to attacks that involve wall-digesting enzymes like PG may be similar in the plant-pathogen and plant-insect interactions (CA). Studies of the signaling roles of pectin-derived oligosaccharides (PDOs) in regulating fruit ripening and plant responses to insects and pathogens (CA). Studies with tomato fruit having transgenically suppressed PG and expansin gene expression indicate that the fruits have modified cell wall digestion and soften slightly less than wild-type fruit. Studies of mealy texture during the ripening of chilled peaches are examining ripening-related cell wall metabolism in terms of polysaccharide structure change and enzyme activities (CA).

    Activities of antioxidant enzymes have been studied in relation to susceptibility of fruit to superficial scald. No consistent relationships were identified (NY, Ithaca). To determine how synthesis of α-farnesene in apple fruit is regulated, genes encoding key enzymes of the biosynthetic pathway are being cloned and characterized (MD-USDA).

    Work has continued to understand the mechanism by which DPA reduces superficial scald (a form of chilling injury). DPA inhibited oxygen, decreased membrane potential, and negated the uncoupling effect of 1040DNP (GA). Use of a chromotropic nitrone spin trapping agent showed the presence of two principal farnesyl-nitrone adducts is related to development of scald in apples (WA). Several tomato lines transformed with an antisense construct of a phospholipase D (PLD cDNA bore fruit with 75-80% lower PLD mRNA than wild-type fruit (MD-USDA). Data indicate that HMGR1 is not a regulatory step in -farnesene biosynthesis, and its expression is greatly enhanced by low O2 (MD).

    A clinical feeding trial indicated that watermelon lycopene is bioavailable to humans without a heat treatment (OK).


    Future Work

    We will continue work evaluating materials from the NE-183 cultivar trials, and emphasis on postharvest handling of Honeycrisp will continue. An emphasis on reducing storage disorders and improving the flavor and nutritional quality of fruit will guide our studies. We will continue to evaluate the benefits and risks of using 1-MCP on apples, pears and other fruits to extend storage life, reduce handling costs and improve fruit quality. Alternative methods to control decay and insects on fruit crops after harvest will continue to be studied, including sanitation measures, safer chemicals, controlled atmospheres, heat treatments and biological control. The biology underlying the various fruit characteristics and disorders will continue to be studied to increase our understanding so as to improve our ability to develop effective control measures, such as development of resistant cultivars.

    Impact Statements:
    1. Information generated should help the apple industry fine tune their postharvest practices and increase the quality of fruit sent to market
    2. Because PGIP can provide a degree of biological enhancement of resistance to pathogens and, perhaps, amelioration of insect damage, use of PGIP (either through molecular approaches or as a selection guide in conventional breeding programs) may reduce the use of chemical control agents in the field and postharvest.
    3. Learning the best time to harvest these new cultivars for flavor and storage potential and their probable storage lives makes it less risky for apple growers to try new cultivars which appeal to consumers. Disease resistance in some new cultivars benefits growers as well
    4. Reduction of postharvest application of chemicals and drenches reduces costs and also benefits the environment.
    5. Increasing calcium concentration in apples improves quality and storage life.
    Last Modified: unknown

    Date of Annual Report: 06/24/2003

    Report Information:
  • Annual Meeting Dates: 06/11/03 to 06/12/03
  • Period the Report Covers: 10/2002 to 09/2003

    • Participants:
    Brief Summary of Minutes of Annual Meeting:


    URL: Copy of minutes

    Accomplishments:
    Several are working with Honeycrisp apples, focusing on crop load, harvest maturity, delayed cooling, storage temperature and CA regimes (NS). A postharvest delay in cold storage treatment has been developed for Honeycrisp apples that will eliminate soft scald and soggy breakdown development (MA, NY-Ithaca, NS). Evaluation of storage potential of Golden Supreme, Shizuka, Cameo, Ambrosia and Pink Lady continue (MA, BC).

    Polyphenolics from six plum cultivars applied to two human cancer cell lines showed antiproliferative activities in a dose-dependent manner. French Damson plums showed the highest growth inhibitory effects, whereas Stanly showed the lowest. There was a good correlation between total phenolics and IC50 values (NY-Geneva).

    During storage of Bartlett pears, if fruit were stored at -1:C, there was no need to scrub ethylene from the environment. (CA).

    Harvest maturity of Gala effects fruit response to 1-MCP (NC). It has been shown that delays before treatment of up to 8 days can reduce but not eliminate the effectiveness of 1-MCP on maintenance of fruit quality (NY-Ithaca). For British Columbia apples, 1-MCP had to be applied early to be effective. 1-MCP reduced scald in air-stored Granny Smith, Delicious, McIntosh, Spartan and Fuji and was less effective than CA storage in controlling scald. 1-MCP increased soft scald in CA-stored fruit (BC).

    1-MCP can be effective on both McIntosh and Cortland apples; contrary to some previous reports. Its efficacy on both cultivars is not improved with a second application (NS). 1-MCP treatment substantially reduced superficial scald development on McIntosh and Cortland, and eliminated it on Delicious, thus eliminating the need for chemical control of scald through post harvest drenches (MA)
    .
    Hydrophobic volatile production in 1-MCP-treated Delicious apples was similar or exceeded the control after storage, while it was non-existent in 1-MCP-treated Gala. Superficial scald development in Delicious was reduced significantly by 1-MCP. (ONT).

    A split application of ReTain has more effect on maturity of Gala than a single application. When 1-MCP is applied to ReTain treated fruit the effects are greater than when either compound is used alone (NC). No significant benefit from pre-harvest ReTain application has been observed on Empire over the past 4 years. Use of DPA to control CO2 injury could be eliminated provided Empire apple fruit were harvested at proper maturity, treated with 1-MCP and stored in low O2 CA with levels of CO2 below the recommended 2% (ONT).

    There was no significant difference in disease incidence between 1-MCP-treated and non-treated apples that had been wounded and inoculated with P. expansum or TBZR Botrytis cinerea. However, in wounded non-inoculated Empire apples variable natural decays were observed. With the exception of apples stored in air, a higher percentage of decays were observed in 1-MCP-treated apples. No significant antagonistic interaction was observed between 1-MCP and SCHOLAR and MERTECT treatments, and better control of blue mold was achieved with SCHOLAR on 1-MCP treated apples (ONT).

    Decay of wound-inoculated Golden Delicious apples by Colletotrichum acutatum or Penicillium expansum during and after 0 0C storage was prevented by heat treatment at 38 0C for four days in combination with a heat tolerant biocontrol agent (yeast species). Sodium bicarbonate alone had no benefit but improved the efficacy of the biocontrol agents without heat treatment (USDA-MD).

    For 1-MCP treatment of Bartlett pears, it is critical that fruit be harvested and treated with 1-MCP at optimum maturity (ONT). Harvest maturity influences the response of Bartlett pears to 1-MCP, but fruit can be treated after a period of cold storage if they have not initiated the climacteric (CA). The lack of any 1-MCP effect on the two highbush blueberry cultivars studied shows that 1-MCP is not beneficial to all horticultural crops (NS).

    Tests of diffusion of 1-MCP through fiberboard boxes and plastic liners containing tray packed apples showed that 16 hours was sufficient for the 1-MCP to reach all apples in all trays. Smoke machines were used to test air tightness of tractor trailers for 1-MCP treatment. Doors seals had to be improved to achieve at tight container (NC).

    Researchers in Nova Scotia have discovered that chlorophyll fluorescence can be used to determine the lowest acceptable oxygen concentration in chlorophyll-containing fruits. A chlorophyll fluorescence system (HarvestWatch) has been developed with a commercial partner (Satlantic Inc.) that can be used to continuously monitor fruits under CA conditions and control the oxygen at its lowest acceptable concentration (NS).

    Diphenylamine and ethyoxyquin were shown to reduce skin browning of Bartlett pears subjected to vibration. Susceptibility to skin browning is related to fruit firmness (CA).

    Various alternative treatments to control insects after harvest are under investigation. Radio frequency heating controls insect pests in walnuts and almonds with no negative effects on kernel quality (CA). Hot water treatments control codling moths in sweet cherry but stem browning may limit application. Radio frequency heating may show more promise (CA). A GRAS fumigant, ethyl formate, shows promise for control of insect pests on table grapes; when used immediately following SO2 fumigation, grape tolerance is good (CA).

    Objective 3: To expand fundamental knowledge to improve and create new technologies to assure high quality and wholesomeness of fruit and enhance market
    opportunities

    A comparison of the effects of MCP, 1.5% O2, and MCP + 1.5% O2 showed that the latter treatment was more effective in inhibiting the onset of the ethylene climacteric and suppressing ACS and ERS1 transcripts. The combined application of MCP and 1.5% O2 was very effective in retarding the onset of the climacteric in Granny Smith apples held at 6˚C for 203 days, and inhibiting the accumulation of ACS transcripts. Treatment of apples with MCP, 1.5% O2 and MCP plus 1.5% O2 at different stages showed that the latter treatment was more effective in inhibiting the rate of C2H4 evolution and suppression of accumulation of ACS and ERS1 transcripts. None of the treatments affected the expression of ACO (MD). Data suggest that our strategy to extend storage life of apples through down regulation of ethylene production provides a viable alternative to controlled atmospheric storage (NY-Geneva).

    Suppression of tomato fruit PG or Expansin synthesis improves the consistency characteristics of processed juice (i.e., paste). Interestingly, over-expression of Expansin also improves paste consistency. Several monoclonal antibodies that recognize cell wall pectin epitopes have been used in immunohistochemical studies to characterize cell wall changes in peaches that are ripening normally and those that are ripening to a mealy texture (CA).

    In order to elucidate the functions and regulation of the PKS genes in raspberry, we are determining the number of aromatic polyketide synthases expressed during raspberry fruit ripening by molecular and proteomic studies. (NY-Geneva).

    Partial cDNAs encoding one phospholipase D (PLD) and two lipoxygenase (LOX) genes were cloned from muskmelon. Transcript levels of these genes as well as PLD and LOX enzyme activities in muskmelon fruit tissues were evaluated over the course of development and postharvest storage. PLD and LOX are thought to be involved in loss of membrane integrity during muskmelon fruit ripening and senescence (USDA-MD).

    Studies on the mechanism of chilling injury and involvement of the electron transport chain in the mitochondria in oxidative stress reactions continued. A 4-fold increase in the size of the ubiquinone pool was seen in mitochondria isolated from green bell peppers stored at 1 C compared to those stored at 20 C. Most of the increase was in ubiquinone-6. Ubiquinones may also be involved in stabilizing membranes in much the same manner as the sterols, such as cholesterol, and the lipid soluble antioxidants, such as α-tocopherol (GA).

    A terpene synthase cDNA from scald-prone Law Rome apple was functionally expressed in E. coli and proven to encode an α-farnesene synthase. A complete genomic clone was obtained for HMG2 from Law Rome, a gene thought to encode an isozyme of hydroxymethylglutaryl-CoA reductase that initiates α -farnesene synthesis in apple peel tissue. Knock outs of these genes will prove or disprove the hypothesis that α -farnesene and its oxidation products are directly involved in induction of superficial scald on apple fruit (USDA-MD).

    Use of a chromotropic nitrone spin trapping agent determined the role of active oxygen species in apple scald development. Occurrence of reacted spintrap appears to be correlated with scald severity. Two major species of nitrone-trapped radicals related to farnesene oxidation were noted with the highest seen in fruit from RA storage that scalded severely. The amount of radicals trapped needs to reach a certain level before symptoms occur. Inhibition of apple farnesyl protein transferase, a major signal transduction protein resulted in increased levels of farnesene (WA). Differential display analysis between Granny Smith, a scald sensitive cultivar, and Gala, a resistant one, resulted in the isolation of cysteine protease cDNA which is expressed only in the peel of Granny Smith fruit (MD).

    Researchers in Oregon and California are generating Botrytis-resistant tomato plants using the resistant nightshade Solanum lycopersicoides. They expect that introgression of Botrytis resistance will reduce the use of fungicides to control a pathogen that is resistant to a variety of chemicals. They hope to identify QTL and eventually genes that confer disease resistance (OR). An assortment of pectin-derived oligosaccharides has been isolated from lesions caused by B. cinerea development on tomato fruits. These are to being structurally characterized and will be tested for biological activity (CA). Separate transgenic tomato lines with suppressed and over-expressed endogenous PGIP genes have been generated to test the idea that PGIP interaction with pathogen PGs leads to the production of oligosaccharide defense signals (CA).

    Future Plans

    Our new project proposal includes two new objectives that increase the focus on fruit flavor and nutritional quality and developing recommendations for the use of 1-MCP. We will continue to evaluate new and existing cultivars to determine the best methods of postharvest handling. This will include collaboration with NE183 trials and an emphasis on Honeycrisp and Ambrosia, two popular apples with postharvest challenges. We will continue to evaluate the benefits of 1-MCP application to apples and increasingly to other fruit. Commercial application methods for small-scale growers will be refined. We will continue to evaluate transgenic apple fruit with reduced ethylene synthesis and will explore the relationship between ethylene production and flavor volatile synthesis. The effects of postharvest handling and cultivar on fruit flavor and nutritional value will be explored. We will continue our study of the biology of storage scald to understand the difference between susceptible and resistant cultivars. There will continue to be emphasis on developing safer chemical or non-chemical methods to control disease and insects after harvest to improve the safety and quality of fruit.

    Impact Statements:
    1. If delayed cold storage continues to reduce storage disorders of Honeycrisp apples, industry can proceed with further production and marketing of this highly profitable cultivar without fear of losing the crop due to disorders appearing after harvest.
    2. Learning the best time to harvest new cultivars for flavor and storage potential and their probable storage lives makes it less risky for apple growers to try new cultivars which appeal to consumers.
    3. Successful use of 1-MCP will reduce postharvest application of scald control drenches thereby reducing costs and also benefiting the environment. Longer maintenance of fruit firmness allows greater marketing flexibility and higher quality fruit for consumers.
    4. 2. The rapidly expanding pomegranate industry in California is using the results of our research in controlled atmosphere storage of pomegranates (5% O2 + 15% CO2 at 7.5oC and 90-95% relative humidity) to extend their marketing period.
    5. Understanding the genetic basis of scald susceptibility in apples or mealiness development in peaches can lead to methods of control or development of resistant cultivars through genetic engineering or traditional breeding.
    Last Modified: unknown
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