SUMMARY Nicotiana rustica tissue cultures derived from seeds or embryos infected with cherry leaf roll virus (CLRV), remained infected after culture at 22 oC. No infectivity was found in cultures held at 32 oC for 5 days but it was readily detected after such cultures were transferred to 25 oC for 8 days. Virus was permanently eradicated from most plants after 20 days incubation at 32 oC and from all plants after 7 days incubation at 40 oC.Partially purified preparations of CLRV lost infectivity after 9–12 days at 22oC, 5 days at 32oC and 3 days at 40oC.

Cucumber mosaic (CMV) and alfalfa mosaic (AlfMV) viruses were eradicated or their concentrations greatly diminished when infected meristem tips were grown in static or shake culture at 32 or 34 "C. Similar cultures grown at 22 "C remained infected. Tobacco mosaic virus (TMV) was not eradicated from shake cultures at 32 "C and the concentration of TMV in such cultures at 32 "C was sometimes higher than at 22 "C.The concentration of CMV and AlfMV was considerably less in cultured tissues than in infected leaf material, but that of TMV was similar. Cultures infected with CMV or TMV grew more slowly than healthy cultures. Growth of AlfMV infected and healthy cultures was similar.

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