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Effect of Alternating Temperature Regimes on Reduction or Elimination of Viruses in Plant Tissues. Hector Lozoya -Saldana, Graduate student, Department of Plant Pathology and Cell Interaction Group, University of California, Riverside 92521; W. O. Dawson, associate professor of plant pathology, Department of Plant Pathology and Cell Interaction Group, University of California, Riverside 92521. Phytopathology 72:1059-1064. Accepted for publication 30 December 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1059.

The effect of environmental temperature regimes alternating between optimal and restrictive temperatures on reducing or eliminating virus in tobacco mosaic virus (TMV)-infected tobacco or cowpea chlorotic mottle virus (CCMV)-infected cowpea was examined. Infected plants were incubated in temperature regimes that were alternated 4 hr at 40 C and 4 hr at 25 C, 6 hr at 40 C and 2 hr at 25 C, or 4 hr at 45 C and 4 hr at 25 C. The alternating temperatures allowed host growth whereas constant restrictive temperatures did not. These temperature regimes greatly reduced the accumulation of TMV in inoculated and newly developing leaves. However, TMV moved into and multiplied in newly developing plant parts and treatment did not facilitate obtaining plants free of virus by tip culture. The alternating temperature regimes more severely limited CCMV, reducing virus in some leaves below detectable levels. Although CCMV moved into and multiplied in some newly developing tissue, large areas were free of virus as demonstrated by a high percentage of virus-free plants which were obtained from 2- to 5-cm-long shoot segments. Alternating temperature regimes also affected the production of symptoms by both viruses. Leaves that developed in the temperature regimes had either milder or no symptoms and some that normally were symptomless developed unusual symptoms.