Effects of temperature on the Tm-1 gene for resistance to tobacco mosaic virus in tomato

Abstract

In tomato plants grown at constant temperatures from 20 to 35 °C, the Tm-1 resistance gene was completely effective in suppressing symptom formation by tobacco mosaic virus (TMV) strain 0. In contrast, inhibition of virus multiplication by the gene was strongly temperature-dependent; in plants heterozygous for Tm-1 it was over 95% at 20 °C but only 20% at 33 °C. Although TMV multiplication in both susceptible and resistant plants was reduced at very high growth temperatures, it is suggested that this general effect of temperature is distinct from its specific effect on Tm-1 controlled inhibition of virus multiplication. TMV strain 1 caused symptoms on Tm-1 plants; the higher the temperature, the more severe the symptoms. Strain 1 multiplication in both susceptible and resistant plants was much more temperature sensitive than was strain 0 multiplication and this tended to obscure the effects of temperature on the action of the Tm-1 gene with respect to strain 1 multiplication. However, the results indicate that strain 1 multiplication is inhibited by Tm-1 at 25 °C but not at 33 °C. Experiments in which Tm-1 plants infected with strain 0 were transferred from high to low temperature suggested that the anti-multiplication activity of Tm-1 was quickly restored at the lower temperature. Under this temperature regime, strain 0 did overcome the symptom suppression function of the gene.