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  • Author or Editor: Diane M. Varga x
  • Journal of the American Society for Horticultural Science x
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`Columbia' and `Gebhard' strains of red `d'Anjou' pears (Pyrus Communis L.) harvested at similar maturity exhibited different ripening behavior after monthly removal from 1C storage in air. `Columbia' fruit produced ethylene at higher rates than `Gebhard' fruit during 15 days of ripening at 20C after each corresponding storage interval, `Gebhard' fruit required a longer period of chilling than `Columbia' fruit to generate noticeable rates of ethylene during ripening. The unripened fruit of both strains contained similar amounts of ACC at each corresponding storage interval. At each corresponding ripened state, ACC content in `Columbia' fruit increased 2 to 3-fold, while that in `Gebhard' fruit changed very little. After sufficient chilling, `Columbia' fruit were capable of softening to proper ripeness, and they developed buttery and juicy texture as indicated by the apparent reduction of extractable juice (EJ) content. `Gebhard' fruit also softened but to a lesser extent than `Columbia' fruit. Ripened `Gebhard' fruit had only slightly lower levels of EJ than unripened fruit and did not develop a buttery and juicy texture after any storage intervals. Titratable acidity (TA) in fruit of both strains varied between for the 1988 and 1989 seasons but decreased significantly during storage in both years. Soluble solids concentrations (SSC) in both strains also varied seasonally but did not change during storage or ripening. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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A proportion of `d'Anjou' pear fruit (Pyrus communis L.) developed a disorder, “black speck” or “skin speckling”, after prolonged controlled atmosphere (CA) storage (1% O2, - 0.5 C). A comparative study of biochemical components revealed that there was no significant difference in succinic, citric, fumaric, and pyruvic acids between the speckled' and normal skin tissues. The content of malic acid in the affected tissue was almost three times lower than that in the normal tissue. The specific activity of NADP-malic enzyme (EC in the affected tissue was also lower, but the total activities were similar. The affected tissue contained higher percentages of dry matter and soluble proteins than the normal tissue. Two-dimensional gel electrophoresis of proteins showed that two groups of novel polypeptides appeared only in the affected skin tissue. This study indicated that a certain proportion of `d'Anjou' pear fruit might have been exposed to unfavorable preharvest environmental stresses, and, therefore, could no longer tolerate the subsequent semi-anaerobic and chilling stresses during prolonged CA storage.

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