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Effect of Temperature, Plant Age, and Infection Site on the Severity of Crown Gall Disease in Radish. L. W. Moore, Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Oregon 97331; David T. Tingey, Plant Physiologist with the Environmental Protection Agency, Corvallis, Oregon 97331. Phytopathology 66:1328-1333. Accepted for publication 31 March 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1328.

Radish growth was retarded by crown gall as measured by leaf area, dry weight, and the rate of leaf initiation (Plastochron Index). The largest growth reduction from crown gall was temperature-dependent and occurred at the same temperatures that maximized top growth of noninfected control plants (day/night temperatures of 30/26 and 34/30 C). Crown gall had little effect on plant growth at 14/10 C. Growth retardation at 30/26 and 34/30 C begins within 2 days after inoculation as shown by the Plastochron Index. Significant differences in plant growth occurred when various sites on plants were infected. Total dry weight reduction was greatest when the upper hypocotyl was infected. Growth reduction was most severe when younger plants were inoculated regardless of the infection site. Young plants infected in the upper hypocotyl were permanently stunted, and failed to recover after an extended growth period.

Additional keywords: Agrobacterium tumefaciens.