On the composite nature of certain potato virus diseases of the mosaic group as revealed by the use of plant indicators and selective methods of transmission
Evidence is presented which proves that many of the potato virus diseases known as mosaic, crinkle and streak are composite in nature. A technique of virus isolation from a complex in the living plant is described. The methods of virus isolation fall into 3 groups and separation was effected by (1) utilizing the selective powers of virus transmission exhibited by the aphis Myzus persicae; (2) the use of plant indicators and plant filters; and (3) taking advantage of the different rates of movement of the constituent viruses of a complex in the tobacco plant. 2 viruses, x and [gamma], isolated from a symptomless "streak" carrier potato, Up-to-Date, are described, and their reactions upon a selected range of host plants are given. The virus [gamma]is transmissible by needlescratch but not by aphids; the virus [gamma] is transmissible by both methods. The virus y has been shown to be an almost invariable constituent of potato virus diseases of the mosaic group; it has been isolated from 20 examples of potato diseases of this group, and has also been found apparently alone, causing "crinkle" in several potato varieties.