Zur Frage Des Einflusses Von Röntgen- Und Uv-Strahlen Auf Die Mutationsrate Des Tabakmosaikvirus Nach Bestrahlung Reiner Präparate

Summary

Pure solutions of TMV were irradiated with x-rays or ultraviolet light in order to study possible effects on the mutation rate of the virus. If no spontaneous mutations were observed in a particular virus preparation, no induced mutations resulted from irradiation. In preparations showing spontaneous mutations, the „rate of mutation“ was increased by irradiation only if the exposed material was compared with unirradiated virus diluted so as to give more lesions per leaf than the irradiated sample. The apparent mutation rate increased with dilution of active virus, whether this dilution was effected by irradiation or by the direct addition of phosphate buffer. Artificial unequal mixtures of two related virus strains, with either in the majority, were tested at different dilutions of the whole; without exception the symptoms of that partner present in minority became relatively more frequent with decreasing total concentration of the mixture.

The effects observed here, as well as those described byGowen (1941), can readily be explained on the basis of competition between related virus strains. The evidence does not support an hypothesis of mutagenic action of irradiation on purified TMV preparations.