Abstract
Some properties of two temperature-sensitive mutants of tobacco rattle virus are described. Experiments with mixtures of long and short particles from the mutants and the wild-type (CAM) strain showed that both mutations are in the RNA of the long particle. The mutants could not be distinguished from each other or from the wild-type virus by heat inactivation, serology, particle length or symptoms produced in a range of host plants under normal glasshouse conditions. One of the mutants was temperature-sensitive in local lesion formation in Chenopodium amaranticolor, and in production of infectious virus and RNA in Nicotiana clevelandii, whereas the other appeared to be temperature-sensitive only in C. amaranticolor. Some possible reasons for this behaviour were investigated.