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M. Ahmedullah, M. E Patterson, and G. Apel

Table grapes cvs. Flame Seedless, Black Monukka and Canadice and blueberries cvs. Bluecrop and Northland were exposed to chlorine dioxide (C102) gas under laboratory conditions. Chlorine dioxide was generated chemically. Grapes were fumigated in a plexiglass chamber with C102 for 30 minutes, packed in TKV lugs with Botrytis inoculum planted among the clusters and stored at 0° C for 8 weeks. Blueberries were consumer packed with 5, 10, and 15 gr. Absorb (C102 generator) in Tyvex sachets, enclosed in pillow-pak bags and stored at 0° C for 75 days and at 20 or 30° C for 16 days.

At periodical intervals, moisture loss, decay and quality parameters were evaluated. Chlorine dioxide caused bleaching and skin injury around the capstem on blueberries but not on grapes. Decay was reduced with C102 treatment but moisture loss increased in blueberries. We could store grapes for two weeks without fungal growth. Storage for longer periods necessitated treatment with higher concentrations of C102 which were not generated under our laboratory conditions.

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M. Ahmedullah, B. Dave, M. E Patterson, and M. A. Sales

Table grapes cvs. Flame Seedless, Black Monukka and Canadice were fumigated with 2 levels of Deccodione smoke tablets for 30 minutes. Grapes were packed in TKV lugs with Botrytis inoculum planted among the clusters and stored at 0° C for up to 9 weeks. Size of smoke particles was determined. Fruit was evaluated at weekly intervals for decay and quality parameters. Deccodione residues on fruit were determined and found to be within acceptable limits set for this chemical. It was possible to store the grapes for up to 4 weeks at 0° C in good condition. Beyond this period effect of fumigation was lost. There was no bleaching of pigments around the capstem as is seen with sulfur dioxide fumigation. Storage for prolonged periods will necessitate increasing the dose of Deccodione tables and/or repeating the fumigation.

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Amber L. Robertson*, Karianne M. Kusner, and Sara E. Patterson

Abscission, an active process resulting in the removal of an organ from the main body of a plant, occurs naturally in response to pathogens, disease, or when the plant part is no longer needed. Several delayed abscission mutants have been identified from the Univ. of Wisconsin T-DNA tagged mutant populations in Arabidopsis thaliana. One of the identified mutants, dab 5-1, is characterized by a delay in abscission causing the floral organs to remain attached past position ten; however, all other plant functions are normal. dab 5-1 has been thought to be involved in the secretory pathway. The present study was conducted to further characterize dab 5-1 expression at the cellular, tissue, and organelle levels using reporter gene constructs, light microscopy, scanning electron microscopy, and RT PCR. dab 5-1 expression was found in the roots, root tips, cotyledons, meristem, abscission zone, and anthers. Early abscission can lead to loss in yield and quality and we believe that understanding genes such as DAB5 will ultimately lead to crop improvement.

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J.W. Sitton, M.E Patterson, and G.W. Apel

Immersion of Anjou pears (Pyrus communis L. cv. Beurre d Anjou) in sodium lignin sulfonate (SLS), a flotation agent used in hydraulic handling of pears, did not cause injury leading to skin browning. Immersion of cut pear slices in SLS discolors pear fruit flesh, but the discoloration derived from SLS pigments does not intensify with time. When the fungicide sodium orthophenylphenate (SOPP) was combined with SLS, necrotic skin mottling occurred with increased immersion times and temperatures. A white precipitate in the SLS SOPP solution accompanied phytotoxicity of pear skin tissue. Acidification of alkaline SOPP solutions (pH 11.3) with 0.01 N HCl down to pH 10 produced mild skin necrosis. Both acid (0.01 N HC1) and alkaline (0.01 n KOH) solutions of SOPP and SLS-SOPP combinations caused browning of pear flesh.

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J.P. Mattheis, J.K. Fellman, P.M. Chen, and M.E Patterson

Synthesis of non-ethylene volatiles (NEV) undergoes significant alterations during the transition from vegetative growth to senescence in apple fruit. This change results in a substantial increase in the production of esters characteristic of ripe apples. The relationship between changes in NEV synthesis and other indicators of physiological and horticultural maturity were investigated using `Bisbee Delicious' apples. Analysis of NEV was conducted using headspace sampling and GC-MS. Aldehydes and alcohols were the largest NEV components from pre-climacteric fruit although several esters were detected. The concentration of all NEV components declined to a minimum prior to the onset of the climacteric rise in ethylene synthesis. Initial detection of 2-methyl butylacetate, the major ester in ripening `Bisbee Delicious' fruit, occurred several weeks prior to the onset of the climacteric. The increase in ester synthesis accelerated during the post-climacteric period and the amount of total aldehydes also increased.

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Xuetong Fan, J.P. Mattheis, M.E. Patterson, and J.K. Fellman

Several strains of Fuji apples were harvested weekly from September through October in 1990 and 1991, and evaluated for maturation and quality after 1 and 7 days at 20 °C following harvest and storage in atmospheres of 0.5%, 1.0%, 2.0% O2 and air. Results showed that Fuji apples have very low ethylene production rates and little firmness loss during maturation. A change in the postharvest respiration pattern preceded the increase ethylene synthesis. Oxygen concentration during storage directly affected apple respiration rate after removal from storage. Ethylene production rates and internal ethylene concentrations indicated that the apples were still in the preclimacteric stage after 7 to 9 months storage at 0.5%, 1.0%, or 2% O2. Fuji apples develop watercore and tend to have a particular type of corebrowing during maturation on the tree, or during and after storage. The cause is unknown.

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X. Fan, J.P. Mattheis, M.E. Patterson, and J.K. Fellman

Total starch and amylose (AM) concentration and a starch index (SI) were determined in `Fuji' apple (Malus domestica Borkh.) fruit from weekly harvests in 1990 and 1991. As apples matured, SI scores increased and total starch and amylose content decreased. The percentage of AM in the total starch decreased as the apples matured. Because KI solutions interact efficiently only with AM, the SI is less reliable in representing total starch during later stages of `Fuji' apple maturation.