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  • Author or Editor: S.M. Blankenship x
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Three percent oxygen significantly delayed and reduced budbreak of fully chilled apple (Malus domestica Borkh.) trees in a greenhouse. When ambient oxygen levels were restored, budbreak occurred normally. Apple trees stored under 3% ± 1% oxygen at 6C for 35 weeks had no detectable bud development in storage. Budbreak and subsequent shoot growth were normal after the trees had been removed from storage.

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Seeds of `Golden Delicious' apple (Malus domestic a Borkh.) were exposed to constant and alternating chilling temperatures. Germination was reduced in seeds treated with 4/11, 4/13, and 4/15 C for 16/8 h, respectively, compared to those treated at a constant temperature (4 C). The 4 C reached 100 % germination after 1600 h, the 4/11 C after 1864 h, and the 4/13 C after 1973 h at 4 c. The 4/15 C never reached complete germination even after 2200 at 4 C. The predominant fatty acids during stratification at constant and alternating temperatures were palmitic, oleic, and linoleic acids. Stearic acid was found at a lower level. Arachidic and behenic acids were only found in constant temperature treatment. There were no significant changes in fatty acid content during stratification at constant and alternating temperatures except that the 4/11 C treatment increased levels of palmitic, oleic, and linoleic acids.

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Apple sooty blotch (SB) is a disease complex caused by Gloeodes pomigina (Schw.) Colby, Leptodontidium sp. and other fungi. This study was undertaken to determine if G. pomigena and Leptodontidium sp. utilize some portion of the apple epicuticular wax as a carbon source for growth. Two isolates of G. pomigena and two of Leptodontidium sp. were used. Isolates were cultured on water agar coated with a thin layer of either nonacosane, ursolic acid, or complete apple wax and an uncoated control. Radial colony growth over a 30-day period was used to assess growth. Preliminary results suggest that G. pomigena differs from Leptodontidium sp. in carbon source preference. Gloeodes colonies were larger when ursolic acid and apple wax were used as a carbon source compared to nonacosane. Leptodontidium isolates grew best on apple wax. Also, growth was greater on nonacosane than ursolic acid. results from laboratory studies were compared to SB severity (percent surface area covered) in the orchard on cultivars of apples where the wax composition was determined. Although fungal genera were not detailed in the orchard, SB severity was positively correlated with the concentration of ursolic acid (r2=0.69) and nonacosane (r2=0.34).

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Apple cuticular wax is the primary environmental interface between the fruit and pathogens or protectant chemicals. Analyses have shown quantitative and qualitative differences in wax of apple cultivars grown in various environments. Of the twelve major wax components, seven exhibited significant variations between Golden Delicious(GD) and Red Delicious(RD) cultivars in all three years. Of these seven components, two compounds occur in greater concentrations in RD than in GD cultivars, one which elutes soon after hexacosanol comprises 10 to 15 % of the RD wax composition verses less than 0.5 % in GD. The other compound comprised 5% of the RD wax verses 1-2% in GD. The other five compounds were found in greater concentrations in GD than RD cultivars. Tetracosanol and another early eluting unknown compound each make up 1 to 3.5 % of GD wax composition while appearing in only trace amounts in RD cultivars. Hexacosanol and a third later eluting unknown each constitute 2 % of GD while concentrations in RD were consistently 1 % or less. Ursolic acid, appears as two isomers, the first isomer constituted 12 to 16 % of GD wax and only 8 to 9 % of RD cultivars. Nonacosane and the major isomer of ursolic add constituted 50 to 70% of the total wax of each cultivar and were not significantly different.

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Mature-green `Grande Naine' bananas from Costa Rica, Mexico, Ecuador, and Guatemala were harvested in June, Sept., and Dec. 1993 and Mar. 1994. Fruit were treated with ethylene and held at 17C and 80% to 90% relative humidity until they reached color 6 of the standard color scale. Guatemalan bananas had the highest respiration rate, followed by Costa Rican, Mexican, and Ecuadoran fruit. Peel color, ethylene production, and soluble solids content did not differ among the countries. Measurements made at arrival in the United States had a low correlation with days to reach color 5. Prediction equations showed significant linear relationships for most variables; however, correlations were very low. The highest coefficient of determination was observed with respiration rate (r 2 = 0.289). Maximum R 2 (0.342) was determined using CO2, C2H4, pH, and soluble solids in the model. pH and soluble solids were good variables to determine the physiological stage of the fruit, and they also detected ripening changes earlier than peel color or firmness.

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