Proceedings of the international symposium, held at Agadir, Morocco, 16—21 January Postharvest physiology, pathology and technologies for horticultural commodities: Recent Van Der Valk, Henry C. Read Article. Share Full Text for Free beta. Web of Science. Let us know here. System error. Please try again! How was the reading experience on this article? The text was blurry Page doesn't load Other:. Details Include any more information that will help us locate the issue and fix it faster for you.
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Try 2 weeks free now. Explore the DeepDyve Library Search or browse the journals available. All the latest content is available, no embargo periods. In situations where regional environmental conditions could influence the outcome of the study but appropriate analytical capability is not available at specific locations, fruit samples will be exchanged among stations. Results obtained from this objective will provide information about the importance of preharvest factors on tolerances of fruit to elevated C02 and low Oz, and is interdependent with Objective 2, in which manipulation of the levels of these two gases will be evaluated for its potential as an alternative to chemical control of diseases, pests and physiological disorders, and Objective 3, in which the underlying biological principles of fruit responses to these gases are to be investigated.
The information derived -from this work will prevent large plantings of inappropriate cultivars, and identify best-management practices for worthy new cultivars. Analyses to determine the composition and amount of volatile compounds will be performed using headspace and purge-and-trap techniques developed by members of the group MI, WA, USDA-WA.
These data will be important to quickly identify cultivars that may be more sensitive to low OZ or elevated C02 concentrations. Integrated with this line of research, MI will perform storage tests using a modified atmosphere packaging approach that will determine tolerance limits to OZ and CO. Tolerance limits to low OZ and elevated CO, will also be established by non-destructive measurements of chlorophyll fluorescence and ethanol production NS.
Collectively, this information is needed to identify the suitability of various cultivars for mixing in CA storage rooms. Cultivars that differ markedly in their low OZ tolerance may require separate storage facilities, or a commitment by commercial producers to create special handling techniques. Data on respiration are needed to estimate cooling demand and relative rates of deterioration. These data may also be useful for modified atmosphere packaging applications in the marketplace. The second major work plan concerns the postharvest evaluation of existing cultivars.
Some overlap of these tasks with those described above exists, as some of the cultivars being evaluated by NE have already been planted extensively throughout North America. Our focus here, however, is to address specific quality issues limiting the storability of several popular cultivars. Again, as the knowledge base expands, information obtained here is expected to integrate with knowledge derived from the fundamentally basic research planned under Objective 3.
Examination of flavor characteristics of Gala apples will be performed as an expansion of previous efforts by NE members. Loss of flavor is a limiting factor for storage of Gala, so a cooperative project between PA and USDA-MD has been established to determine optimum storage conditions to maintain flavor in fruit of this cultivar. Another important project will be reduction of watercore in Fuji apples, as fruit of this cultivar grown in northern North America frequently exhibit this disorder at harvest.
Evidence indicates that preharvest temperatures may affect the propensity of fruit to develop watercore. For example, Fuji apples grown in Washington are very susceptible to watercore, whereas those grown in California show only minor watercore, even though they are harvested at a more advanced maturity. Because Fuji is one of the cultivars grown in the NE trial, fruit will be available from a variety of growing locations for assessment of the effects of preharvest temperatures on watercore development of this cultivar. Collaboration of this type enables us to obtain data on a wide range of temperature conditions quickly for more accurate and rapid model development.
Improving methods to estimate fruit maturity forms the final project under this work plan. Two years of commercial evaluation on McIntosh, Cortland and Jonagold in NS has shown it to be a simple, cheap and accurate method to predict final harvest date for each orchard. It is not known if this index will be universally applicable across all climates represented by locations of NE members, but since, under this objective, the requisite data are continuously acquired for many cultivars of apples, its predictive value at different locations should be easy to assess.
In addition, MI is developing a promising new method for assessing apple maturity, the 'dip-stick' ELISA for ACC oxidase, which is an immunochromatographic assay similar to the pregnancy test. Prototypes of the ELISA should be available for testing by scientists in other states by the season. Extensive inter-regional collaboration is expected in evaluating this technology in relation to other maturity indices. Additional benefits to be realized from progress under this research objective lie in the close coordination with efforts under Objectives 2 and 3.
Examination of many different cultivars will facilitate comparative studies of disorder mechanisms, volatiles associated with disorders, composition and regeneration of flavor compounds, molecular biology, and mechanisms of ripening and softening. Objective 2. To develop sustainable alternatives to chemical control of physiological disorders, diseases, and pests. Within this objective, three avenues of investigation with be undertaken with goals of developing control or management mechanisms for the storage problems of apple and pear scald, fungal decay and insect pests. The focus will be to develop techniques that minimally impact the environment, have the potential to reduce agricultural chemical residues, or provide consumeracceptable alternatives.
Efforts are to be coordinated such that one control strategy does not preclude the use of another. Research for this objective will be 'coordinated by NE committee members who are recognized leaders the indicated research areas. Physiological disorders: Control of superficial scald in apple and pear. We have categorized the means for scald control as targeting either scald avoidance or scald reduction.
In the proposed project, the priority is to focus on the storage disorder of apples and pears known as superficial scald. Promising scald control mechanisms will be integrated with traditional storage protocols and subjected to a systems evaluation. The criteria for evaluation will be ease of transition, profitability, and sustainability of storage strategies.
Avoidance of superficial scald will be studied primarily through the use of predictive tools. The goal is to minimize postharvest chemical usage by predicting when the use of antioxidants is necessary.
Mathematical prediction models developed by the previous project MA require further testing and refinement at various locations throughout the U. A similar dependency of scald on preharvest temperatures will be investigated for d'Anjou pear fruit OR. Relationships between preharvest temperature and scald incidence will be used to generate a mathematical model for scald prediction for pear.
Reduction of scald using non-chemical techniques will be studied using approaches developed by members in the previous NE Project. Continuous low Oz treatments for scald reduction in commercial conditions requires further examination due to problems with off-flavor development in fruit from some locations, especially the Northeast, and variable efficacy of treatment.
In our recently published NE cooperative study Lau et al. A number of independent scald-related projects remain underway with the anticipation that these approaches will be incorporated into larger-scale cooperative projects if promising results are obtained. Important among the more recent findings is that scald control in apple can be achieved by initial low oxygen stress followed by CA storage MI. In future work, the level and duration of initial low OZ stress and subsequent CA conditions will be optimized to safely and effectively control scald without compromising fruit quality for apple MI, NS, NY-I.
Conditions and handling prior to and after the low OZ stress will approximate commercial procedures as closely as is possible. Decay control. We will be continuing our efforts to develop alternatives to persistent agricultural chemicals for postharvest decay control, focusing on the control of P.
Work at USDA-MD and CA is examining the interaction of fungal pathogens and fruit with the aim of identifying factors that can limit the development of decay during storage. The proteins have been purified and the genes for all 3 PGIPs have been cloned. Tests are underway to identify factors that determine which pathogen PG isoforms are selectively inhibited by a specific PGIP.
The pear PGIP has been expressed in transgenic tomato plants in order to test whether increased expression of PGIP can influence fruit susceptibility to pathogens. Researchers at USDA-MD and CA will collaborate by exchanging pathogen strains primarily Botrytis cinerea , antibodies and gene probes, as well as information on protocols and results.
Other control measures to be examined will be confined to those with potential to be integrated into modern handling and storage strategies employing sealed storage construction or sealed packages. With the exception of C02 treatments, these control measures are relatively untested, and are rather exploratory in nature. Therefore, the research does not warrant interaction between numerous participants at this stage. If, however, a technique is considered to have special promise, we anticipate expanding the scale of work and the number of stations involved in efficacy testing.
Optimum levels of OZ and CO. Other approaches using reduced or non-chemical control of biotic disorders include use of hexanal and other aldehyde vapor MI , acetic acid fumigation to control decay of apples PA , and organic aroma volatiles to control decay of sweet cherries ONT-V. Decay incidence will be determined as a function of dose. The possibility of applying the gas in modified atmosphere packages will be explored MI.
Objective 3. Under this objective, members of NE will conduct various lines of primarily basic research aimed at elucidating the biochemical, physiological and genetic bases of postharvest storage disorders, ripening and softening, and the effects of CAs both beneficial and detrimental on quality attributes such as color, aroma, texture and nutritional value.
Some of these studies will utilize molecular genetic techniques to address specific problems or questions, and the long-range goal of much of the research will be to introduce into fruits genetic traits which obviate the need to control decay, disorders, and deterioration of quality with chemical treatments that may pose a human health risk and restrict international sales.
Stress-induced disorders and injuries. As indicated in Objective 2, understanding and controlling scald in apple and pear fruits will be a major focus of NE participants. DPA treatment is costly, is considered a health risk, is environmentally unsound, and necessitates the use of a fungicide to limit decay in storage. Furthermore, all fruit will not tolerate the low level of oxygen required to prevent scald.
Finally, the present control measures are not always effective; sometimes after the fruit are removed from storage scald symptoms arise. Recent research by NE members supports the hypothesis that scald as well as other stress-induced injuries are mediated by active oxygen species AOS. Also, further evidence was found that development of scald is linked with the synthesis and oxidation of the sesquiterpene -famesene.
Thus, future research efforts by the group will center on: 1 investigating the role of AOS in scald induction and of antioxidative defense mechanisms in scald resistance, and 2 elucidating the pathway of alpha-farnesene synthesis and the role of its oxidation products in development of scald symptoms. In addition to comparison of commercially important apple cultivars that are clearly scaldsusceptible e. Analyses of the levels of naturally occurring antioxidants ascorbic acid , glutathione, tocopherols, carotenoids, phenylpropanoids, and simple phenolics and the activities of AOS scavenging enzymes superoxide dismutase, peroxidase, catalase, ascorbic acid peroxidase, glutathione peroxidase and glutathione reductase to resistant and susceptible fruits will be conducted by NY-I, MI, ONT-G, MA, and USDA-MD.
Molecular biology protocols will be employed by NY-I and MI to screen for the presence of antioxidant enzyme proteins by Western blots and their activities on non-denaturing PAGE gels , to determine levels of antioxidant enzyme gene expression by Northern blots using their respective cDNAs as probes and to determine the number of copies of the various antioxidant enzyme genes by Southern blot analysis. This approach is expected to identify the biochemical and enzymatic pathways of AOS metabolism that relate to potentiation or prevention of scald development. It is now apparent that the mitochondrial electron transport chain is a major site for production of AOS.
Factors that regulate production of AOS in fruit tissue will be examined by isolating mitochondria from scald-resistant and scald-susceptible fruit. These will be used to assess the components which autoxidize and the level of reduction of the component pool which reacts with molecular oxygen to produce AOS. Levels of reduced and total ubiquinones are to be determined by HPLC and production of the superoxide anion will be measured.
An exchange of results and protocols with MD is anticipated, as this station plans to test the ability of new porphyrin-based superoxide radical scavengers to reduce or prevent scald development in highly susceptible Granny Smith fruit. A series 9f chemically-tailored spin-trapping reagents that can be used to "fix" and then identify the radicals produced in stressed tissue is being developed at WA. Further efforts will be made to develop novel chemical indicators that react with AOS enabling quantification. The connection between a-famesene metabolism and AOS in the promotion of scald has been elusive, but through the efforts of NE participants a breakthrough appears imminent.
ONT-G is pursuing the pathway of a-farnesene synthesis in apple peel tissue, with the ultimate aim of isolating and characterizing farnesene synthase. Using scald-susceptible apple fruit to clone genes that are induced by low temperature but suppressed by low OZ atmosphere may also provide a cDNA of the farnesene synthase gene MI. This would enable the eventual testing of antisense transgenics for low a-farnesene production and resistance to scald.
The primary oxidation products of a-famesene, conjugated trienes CTs , are much more closely correlated with scald development than a-famesene itself. This raises the possibility that oxidation of a-famesene is enzymatic in vivo.freedotbilosat.tk
Postharvest Physiology and Pathology of Vegetables - Google книги
Should it prove to be the case, the "a-farnesene hydroxylase" would be another target enzyme for genetic regulation to prevent scald. MI has provided evidence for a direct role of a volatile breakdown product of a-farnesene, 6-methylheptenone MHO , in scald development. MHO induced scald-like symptoms in apple peel, tissue sensitivity to MHO increased with time in storage, and in vivo MHO production rose sharply after several months at 0 C in air.
Preliminary results confirm this, and further indicate that autoxidation of CTs is markedly temperature dependent. This could explain why scald symptoms intensify greatly when fruit are rewarmed after long-term storage. Future studies will focus on full elaboration of a-farnesene metabolism, the precise role of MHO in scald induction, and the effects of low O2, ethylene and low temperature on a-famesene synthesis and oxidation.
Comparative studies to identify differences between low-O,,-induced and elevatedCO2-induced fermentative metabolism, and factors affecting the shift from aerobic to anaerobic respiration in whole and fresh-cut fruits, will be carried out at CA. Studies of the roles of pH and copigmentation on stability of internal anthocyanins in strawberries under elevated CO2 as well as the effects of OZ, CO2, and C2H4 on phenolic metabolism and browning of fruit tissues, are planned CA.
Other quality-related biochemical studies will include examination of atmospheric composition-time-temperature interactions on nutritional quality, especially on levels of vitamins A and C, and bioactive compounds such as carotenoids and polyphenols CA. A major effort will continue in the area of flavor biochemistry. Regulation of fruit ripening and softening. The ethylene biosynthesis inhibitor aminoethoxyvinylglycine trade name ReTain is now approved in the U.
NS and WA will evaluate the possible benefits of ReTain on various ripening-associated changes in fruit quality especially softening, and retention and regeneration of flavor compounds after long-term storage and subsequent shelf time. CA will continue to investigate the origin and mode of action of pectin-derived oligosaccharides PDOs , which promote ripening in tomato. This work will utilize the explanted tomato pericarp system that was devised several years ago. NY-G will take a molecular genetic approach to solving the problem of softening in storage in fruit of important apple varieties such as 'McIntosh.
Ethylene production depends on the synthesis of its precursor, 1-aminocyclopropane carboxylic acid ACC , by the enzyme ACC-synthase. Experiments are in progress to transform 'McIntosh' apple with sense or antisense versions of the ACC-synthase gene, with the aim of reducing ACC-synthase activity in the fruit, and thereby reducing ethylene production and consequent softening. A similar strategy will be utilized to achieve a reduction in PGase activity in harvested apple fruit.
Postharvest Physiology and Pathology of Vegetables / Edition 2
The overall goal of this work is to attenuate ripening and softening, and to thereby improve storability. Prediction equations for the occurrence of pre-harvest and storage susceptibility to scald. Monitor CA on a continuous basis in a non-destructive manner using chlorophyll fluorescence.
Develop an equation to predict the amount of DPA needed to control scald in apples in Massachusetts. Determine role of fatty acid esters in scald resistance by virtue of their antioxidant properties.
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Test hypobaric 0. Test pressure infiltration with water or CaCl2 solutions into 'Golden Delicious' fruit transiently to inhibite volatile levels, respiration, and ethylene production by forming a temporary barrier to CO2 and O2 exchange between the fruit tissue and the surrounding atmosphere. Improve the potential for post-storage quality and shelf-life of 'Gala' and 'Golden Delicious' apples by testing at-harvest coating treatments that have relatively high permeability for CO2 and O2 but relatively low permeability for water vapor and fruit volatiles.
Test tray packaging and adequate box ventilation for faster cooling and better quality maintainance of 'D'Anjou' pears during transport and storage. Verify preliminary tests that indicate transformation of strawberry genotypes using pear fruit polygalacturonase-inhibiting protein PGIP gene has been successful. Study bell peppers as a model to support the theory that the major function of the alternative oxidase in stored plant organs is to relieve oxidative stress.
Explain the four unusual phytoalexins that have been identified that seem to be part of the resistance mechanism in scab resistant apple cultivars. Potentially millions of dollars a year in unnecessary chemical use and fruit loss in storage can be eliminated. Longer-term benefits will be derived from obtaining further genetic and biochemical information on physiology and pathological storage disorders, cell wall metabolism, and volatile biosynthesis.
Benefits to the consumer will include less food safety risk through reduced use of chemicals to preserve fruit; longer fruit shelf life, and higher nutritional value at market time. Determine which fruit rot pathogens are selectively inhibited by a specific PGIP. Characterize the metabolism of a-farnesene, the role of MHO in scald induction, and the effects of low O2, ethylene and low temperature on a-farnesene synthesis and oxidation. Develop novel chemical indicators that react with AOS enabling quantification.
Explain the loss of characteristic aroma volatiles in fruit kept in air or CA beyond certain periods of time. Test strategies to slow or stop fruit ripening by anti-sense technology via reduced ACC-synthase or via reduced AGase activity in harvested apple. Describe your bug clearly, including the steps you used to create it. Log In Forgot Password? New User? Project Menu.