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White drupelet disorder of red raspberry Rubus ideaus L.




Hosman, Pamela A., author
Hughes, Harrison G., advisor
Goldsberry, Kenneth L., committee member
Cranshaw, Whitney S., committee member

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White Drupelet Disorder (WDD) is a condition where individual drupelets of red raspberry fruit lack red pigmentation, but are white and fully turgid. This has been associated with high temperature and high UV-B radiation. Five cultivars were evaluated for susceptibility to WDD using UV-B radiation and high temperature (42°C) in a growth chamber. Results of statistical analyses of differences in susceptibility to WDD were mixed but because of possible interactions with date of testing, were determined to be equally susceptible to WDD. Cellulose fibers were used for coating fruit as a potential protectant against WDD. Dry coatings of the fruit were not significantly different from uncoated treatment. However, cellulose fibers applied wet resulted in significantly greater WDD than the control and dry application of fibers. Pigment extracts of red and white fruit were evaluated for responses in color and absorbance level at 535 nm with variations in pH. Extracts from drupelets exhibiting WDD failed to develop red pigment with pH change, thus indicating the absence of the colorless forms of anthocyanins in the fruit. Glucose and sucrose of both red and white drupelets of red raspberry cv. Heritage from field and laboratory samples were analyzed by gas chromatography for soluble sugars. No differences in glucose levels were observed in the red or white drupelets from either field or laboratory samples. However, red drupelets from both field and laboratory exhibited twice as much sucrose as white drupelets.


1992 Summer.
Covers not scanned.
Includes bibliographical references.

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Raspberries -- Diseases and pests
Raspberries -- Effect of radiation on


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