EFFECT OF CYTOKININS ON THE DISEASE RESISTANCE OF TOMATO CULTIVARS TO THE INFECTION OF TOBACCO MOSAIC VIRUS (TMV-T)

The present paper deals with the different effects of the endogenous cytokinins, namely, those of lower R_1 values (L-CTKs) (R_f=0.0—0.5) and those of higher R_1 values (H-CTKs) (R_f=0.5—1.0) on the disease resistance and symptom expression of tomato plants after infection by TMV-T. After the infection of TMV-T, H-CTKs in susceptible tomato cultivars were increased markedly, but not in the resistant cultivars. However, the level of L-CTKs was much higher in resistant cvs than in susceptible ones. Such difference was considered to be used as one of the criteria for the preliminary determination of disease resistance of tomato plants to TMV-T. The application of prepared H-CTKs onto the healthy tomato leaves induced a series of symptoms, including green islands, while the application of TMV tolerance inducer NS-83 caused a raise of the level of L-CTKs to that of resistant cnltivars. It is, therefore, inferred that L-CTKs might be indirectly related to the resistant genes, while H-CTKs to the genes controlling the symptom-expression, however, the mechanism of which remains to further investigation.