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Physiology and Biochemistry

Induced Resistance to Ozone Injury of Soybean by Tobacco Ringspot Virus. R. H. Vargo, Former Graduate Student, Department of Plant Pathology and Center for Air Environment Studies, The Pennsylvania State University, University Park, PA 16802, Present address of senior author: Boyce Thompson Institute for Plant Research, 1086 North Broadway, Yonkers, NY 10701; E. J. Pell(2) and S. H. Smith(3). (2)(3)Assistant Professor, and Professor and Department Head, respectively, Department of Plant Pathology and Center for Air Environment Studies, The Pennsylvania State University, University Park, PA 16802. Phytopathology 68:715-719. Accepted for publication 11 November 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-715.

Soybean plants, 12-18 days after sowing, were inoculated with tobacco ringspot virus (TRSV) on one primary leaf at 4, 6, 8, or 10 days before a 4-hr exposure to ozone at 697 or 797 μg/m (0.35 or 0.40 ppm). Primary leaves of virus-inoculated plants became more resistant to ozone injury with increasing time after inoculation. Ozone resistance was more closely correlated to extent of TRSV-induced apical necrosis than to time after inoculation. The TRSV-induced apical necrosis required for a significant reduction in ozone sensitivity occurred prior to the detection of virus in the noninoculated primary leaves. Leaf conductances were similar in primary leaves of virus-infected and noninfected plants before an ozone exposure; during the exposure, conductances decreased more rapidly in infected plants, but conductances of noninfected plants were similar at the end of the 2-hr exposure. Although TRSV influenced stomatal response to ozone, this effect did not appear to be the primary factor associated with the induced resistance to ozone.