On the interactions of two strains of a plant virus; experiments on induced immunity in plants

Abstract

The author isolated 2 strains of aucuba mosaic of tomato, AG causing green mottling, AY causing yellow mottling. Apart from severity of mottling, the 2 strains retained the properties of the source material, and exhibited little or no mutability. When inoculated into tomato and Zinnia each strain inhibited development of the symptoms of the other strain subsequently inoculated into the same plants. The yellow strain resembled Johnson''s tobacco virus 6, and both yellow and green strains differed from John-son''s tobacco virus 1 in the same manner as the original aucuba source material. Similarly tobacco virus 1, Valleau''s ring mosaic virus, and tomato streak virus immunized tomato plants against subsequent inoculations of the author''s yellow and green aucuba mosaic strains. The X virus of potato and the virus of spotted wilt of tomato had no such protective action against the aucuba mosaic strains. When a plant is inoculated with 2 viruses: (a) one may completely prevent multiplication of the other; (b) one may permit multiplication but inhibit symptom expression of the other; (c) both may multiply, each producing its characteristic symptoms; or (d) both may multiply, producing a cumulative disease more severe than that caused by either virus alone.