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Respiration, Organic Acid, and Sugar Composition of Apple Fruits Collected from Apple Mosaic Virus- or Russet Ring Virus-Infected Trees. J. S. Makarski, Graduate Research Assistant, Department of Plant Pathology, University of Massachusetts, Amherst 01002, Present address of senior author: Department of Biology, Alliance College, Cambridge Springs, Pennsylvania 16403; G. N. Agrios, Department of Plant Pathology, University of Massachusetts, Amherst 01002. Phytopathology 63:1483-1488. Accepted for publication 21 May 1973. DOI: 10.1094/Phyto-63-1483.

Respiration, organic acid content, and sugar content were determined for apple fruits collected from healthy trees and from trees infected with either apple russet ring virus (RRV), which causes both foliar and fruit symptoms, or with apple mosaic virus (AMV), which induces only foliar symptoms. Fruits were collected at monthly intervals during two growing seasons from healthy and AMV- or RRV-infected McIntosh trees. No differences in respiration were detected between healthy and diseased fruits. Virus infection did not hasten or delay the onset of the respiratory climacteric in mature fruit, although there was an indication of a virus-induced increase in the height of the climacteric. Virus infection did not result in the appearance of any detectable new acids: the content of malic acid, one of the two major acids present, was slightly decreased by virus-infection; there was no apparent change in the quinic acid concentration of the infected fruits. Likewise, there was no effect of virus infection on the content of glucose, sucrose, or fructose, the three main sugars found in apple fruit.