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Enhancement of Tobacco Mosaic Virus Spread in Mechanically Inoculated Leaves by Pre-incubation at a Nonpermissive Temperature. W. O. Dawson, Assistant Professor, Department of Plant Pathology and Cell Interaction Group, University of California, Riverside 92502; D. E. Schlegel, Professor, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 66:625-628. Accepted for publication 10 November 1975. DOI: 10.1094/Phyto-66-625.

In tobacco leaves mechanically inoculated with TMV and pre-incubated at temperatures nonpermissive for virus synthesis, the rate of TMV synthesis upon shift to a permissive temperature was markedly greater than that in control leaves. Pre-incubation of infected leaves at 10-12 C inhibited virus synthesis most effectively and subsequent transfer to 25 C produced the most rapid rate of virus multiplication. The optimum duration of pre-incubation was 10 days. In leaves that were pre-incubated at 12 C for 10 days after mechanical inoculation, infectivity increased exponentially from the time of the temperature shift until about 16 hours at 25 C and linearly from 16 hours until 3-4 days at 25 C when the maximum level of virus was attained. The maximum level of virus accumulated in control leaves only after 10 days. Pre-incubation at 12 C enhanced cell-to-cell spread of virus either while at the nonpermissive temperature or immediately after the temperature shift.